Patent Application
20230058935
Embodiments of the disclosure relate generally to multithreaded processes and more specifically to managing return parameter allocation for threads.
Various computer architectures, such as the Von Neumann architecture, conventionally use a shared memory for data, a bus for accessing the shared memory, an arithmetic unit, and a program control unit. However, moving data between processors and memory can require significant time and energy, which in turn can constrain performance and capacity of computer systems. In view of these limitations, new computing architectures and devices are desired to advance computing performance beyond the practice of transistor scaling (i.e., Moore's Law).
Software multithreading allows for duplication of processes (e.g., using the Unix fork command). Data is communicated between processes using inter-process communication methods, such as pipe. Additionally, processes may be coordinated by having one process wait for another process to complete.
The disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure. The drawings, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only.
To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.
Recent advances in materials, devices, and integration technology can be leveraged to provide memory-centric compute topologies. Such topologies can realize advances in compute efficiency and workload throughput, for example, for applications constrained by size, weight, or power requirements. The topologies can be used to facilitate low-latency compute near, or inside of, memory or other data storage elements. The approaches can be particularly well-suited for various compute-intensive operations with sparse lookups, such as in transform computations (e.g., fast Fourier transform computations (FFT)), or in applications such as neural networks or artificial intelligence (AI), financial analytics, or simulations or modeling such as for computational fluid dynamics (CFD), Enhanced Acoustic Simulator for Engineers (EASE), Simulation Program with Integrated Circuit Emphasis (SPICE), and others.
Systems, devices, and methods discussed herein can include or use memory-compute systems with processors, or processing capabilities, that are provided in, near, or integrated with memory or data storage components. Such systems are referred to generally herein as CNM systems. A CNM system can be a node-based system with individual nodes in the systems coupled using a system scale fabric. Each node can include or use specialized or general purpose processors and user-accessible accelerators with a custom compute fabric to facilitate intensive operations, particularly in environments where high cache miss rates are expected.
In an example, each node in a CNM system can have a host processor or processors. Within each node, a dedicated hybrid threading processor can occupy a discrete endpoint of an on-chip network. The hybrid threading processor can have access to some or all of the memory in a particular node of the system, or a hybrid threading processor can have access to memories across a network of multiple nodes via the system scale fabric. The custom compute fabric, or hybrid threading fabric, at each node can have its own processor(s) or accelerator(s) and can operate at higher bandwidth than the hybrid threading processor. Different nodes in a CNM system can be differently configured, such as having different compute capabilities, different types of memories, different interfaces, or other differences. However, the nodes can be commonly coupled to share data and compute resources within a defined address space.
In an example, a CNM system, or a node within the system, can be user-configured for custom operations. A user can provide instructions using a high-level programming language, such as C/C++, that can be compiled and mapped directly into a dataflow architecture of the system or of one or more nodes in the CNM system. That is, the nodes in the system can include hardware blocks (e.g., memory controllers, atomic units, other customer accelerators, etc.) that can be configured to directly implement or support user instructions to thereby enhance system performance and reduce latency.
In an example, a CNM system can be particularly suited for implementing a hierarchy of instructions and nested loops (e.g., two, three, or more loops deep, or multiple-dimensional loops). A standard compiler can be used to accept high-level language instructions and, in turn, compile directly into the dataflow architecture of one or more of the nodes. For example, a node in the system can include a hybrid threading fabric accelerator. The hybrid threading fabric accelerator can execute in a user space of the CNM system and can initiate its own threads or sub-threads, which can operate in parallel. Each thread can map to a different loop iteration to thereby support multi-dimensional loops. With the capability to initiate such nested loops, among other capabilities, the CNM system can realize significant time savings and latency improvements for compute-intensive operations.
A CNM system, or nodes or components of a CNM system, can include or use various memory devices, controllers, and interconnects, among other things. In an example, the system can comprise various interconnected nodes and the nodes, or groups of nodes, can be implemented using chiplets. Chiplets are an emerging technique for integrating various processing functionality. Generally, a chiplet system is made up of discrete chips (e.g., integrated circuits (ICs) on different substrate or die) that are integrated on an interposer and packaged together. This arrangement is distinct from single chips (e.g., ICs) that contain distinct device blocks (e.g., intellectual property (IP) blocks) on one substrate (e.g., single die), such as a system-on-a-chip (SoC), or discretely packaged devices integrated on a board. In general, chiplets provide more production benefits than single die chips, including higher yields or reduced development costs.
As discussed herein, an HTP supports thread creation by executing an instruction that creates and sends a thread create packet. When an executing thread creates a new thread, the existing thread is termed the “parent” thread and the new thread is termed the “child” thread. Both threads execute within the same process and run in a shared memory space. By contrast, different processes run in different memory spaces. The newly created child thread sends a return packet back to the parent thread when the child thread completes. The return packet may contain return values that must have a location where they can be stored until the parent thread executes a join instruction. The parent thread can create different child thread variants depending on if the child thread will have return values and if the parent thread must be paused until the child thread has completed.
A thread create instruction (ETC) specifies a target, a function address, a caller identifier (ID), a call argument count, call arguments, a return argument count, a no-flush flag, a busy-fail opcode, or any suitable combination thereof. Before a thread can be created, space for the return information (also referred to as return arguments or return parameters) is reserved. When a thread eventually completes, the thread writes its return information into the reserved space and waits for the parent thread to execute a thread join instruction. The thread join instruction takes the returned information from the reserved space and transfers it to the parent thread's register state for later usage by the parent thread. Once the child thread is joined, then the reserved space is released.
An ETC instruction can indicate that no return information is returned on completion of the created thread. This indication allows an HTP accelerator to create the thread without reserving space for return information. In this case, a counter is used to keep track of the number of outstanding threads with no return information.
An ETC instruction can specify up to a predetermined number of parameters, each of a predetermined size (e.g., four 64-bit call parameters) that are passed to the accelerator resource. If the created thread targets an HTP accelerator, then the call parameters are written to the child thread's registers (e.g., the child thread's X registers x10-x13 or a0-a3). As used herein, an X register is a portion of a register file that is allocated to a hardware thread. Thus, the thread can access its registers by name and the hardware processing element converts the name to a portion of the register file reserved for the thread.
A target parameter is provided to an ETC instruction that provides information for determining where the target accelerator should be located. For HTP accelerators, the target value may specify which device the new thread is to be started on. For other accelerators, the target device is always the local device and the target parameter is used in an accelerator-specific way to indicate which of the device's local accelerators is to be targeted.
A parent thread executes a join instruction (e.g., EFJ or EFJA) to determine if a child thread has completed, to obtain returned results, or both. In some example embodiments, all accelerator resources (HTP, HTF, and other) use this common approach of returning thread completion status to the initiating parent thread. The returned state from a child thread may include an identifier of the call and the specified number of return parameters. Threads may be created with No Return (NR) specified.
The fiber join (EFJ) instruction joins threads that were created without the No Return indication and ignores threads that were created with the No Return indication. The EFJ instruction processes a single completed child thread and writes the returned caller ID and return information to thread registers of the parent thread for access by the parent thread. In some example embodiments, the Caller ID is a 16-bit value that is provided by the parent thread when a child thread is created. The caller ID is later returned by an EFJ instruction (unmodified) to allow the parent thread to identify which child thread was joined. The terms “thread” and “fiber” are used herein interchangeably, to refer to multitasked threads of execution that share an address space, without regard to the manner in which the threads or fibers implement the multitasking.
The fiber join all (EFJA) instruction has two variants, one that waits for all created threads to complete and one that does not wait. The variant that does not wait provides a status indication and allows the parent thread to continue execution. The EFJA instruction processes all returned child threads and discards all returned values.
All threads that execute on an HTP accelerator eventually complete by executing a thread return (ETR) instruction. A thread that executes an ETR instruction first checks that all thread-initiated operations have either completed or been acknowledged. These operations include: memory stores, atomics and custom atomics, and created threads.
Memory operations where the response does not update thread register state do not cause the thread to stall. A count of the number of memory operations that are outstanding is maintained. A thread that executes an ETR instruction waits for all child threads that it created to complete and all memory operations outstanding to complete before the ETR instruction can complete. Waiting for all memory operations and child threads to complete ensures that a parent thread will not access memory and obtain memory data that is still in the process of being written from a child thread.
Reserving space for return values before creating a child thread ensures that space for the return values will be available when the child thread is ready to store the return values. This prevents costly busy-waiting by threads that have completed processing but are unable to store their return values, preventing other threads from executing. The amount of space reserved could be a fixed size (e.g., four 64-bit values), but this is less efficient than allowing the parent thread to specify the amount of space to be reserved. On-processor memory is limited and its use is reduced when only the amount of space needed is reserved. By comparison with embodiments that reserve fixed amounts of space, using a configurable amount of space for each child thread may allow for more child threads to be executed simultaneously, increasing throughput without increasing hardware resources.
The example of
The CNM system 102 can include a global controller for the various nodes in the system, or a particular memory-compute node in the system can optionally serve as a host or controller to one or multiple other memory-compute nodes in the same system. The various nodes in the CNM system 102 can thus be similarly or differently configured.
In an example, each node in the CNM system 102 can comprise a host system that uses a specified OS. The OS can be common or different among the various nodes in the CNM system 102. In the example of
The CNM system 102 is described herein in various example configurations, such as comprising a system of nodes, and each node can comprise various chips (e.g., a processor, a switch, a memory device, etc.). In an example, the first memory-compute node 104 in the CNM system 102 can include various chips implemented using chiplets. In the below-discussed chiplet-based configuration of the CNM system 102, inter-chiplet communications, as well as additional communications within the system, can use a CPI network. The CPI network described herein is an example of the CTCPI, that is, as a chiplet-specific implementation of the CTCPI. As a result, the below-described structure, operations, and functionality of CPI can apply equally to structures, operations, and functions as may be otherwise implemented using non-chiplet-based CTCPI implementations. Unless expressly indicated otherwise, any discussion herein of CPI applies equally to CTCPI.
A CPI interface includes a packet-based network that supports virtual channels to enable a flexible and high-speed interaction between chiplets, such as can comprise portions of the first memory-compute node 104 or the CNM system 102. The CPI can enable bridging from intra-chiplet networks to a broader chiplet network. For example, the Advanced eXtensible Interface (AXI) is a specification for intra-chip communications. AXI specifications, however, cover a variety of physical design options, such as the number of physical channels, signal timing, power, and so forth. Within a single chip, these options are generally selected to meet design goals, such as power consumption, speed, and so forth. However, to achieve the flexibility of a chiplet-based memory-compute system, an adapter, such as using CPI, can interface between the various AXI design options that can be implemented in the various chiplets. By enabling a physical channel-to-virtual channel mapping and encapsulating time-based signaling with a packetized protocol. CPI can be used to bridge intra-chiplet networks, such as within a particular memory-compute node, across a broader chiplet network, such as across the first memory-compute node 104, or across the CNM system 102.
The CNM system 102 is scalable to include multiple-node configurations. That is, multiple different instances of the first memory-compute node 104, or of other differently configured memory-compute nodes, can be coupled using the scale fabric 106 to provide a scaled system. Each of the memory-compute nodes can run its own OS and can be configured to jointly coordinate system-wide resource usage.
In the example of
In an example, the first switch 110 from the first memory-compute node 104 is coupled to one or multiple different memory-compute devices, such as including the first memory-compute device 112. The first memory-compute device 112 can comprise a chiplet-based architecture referred to herein as a CNM chiplet. A packaged version of the first memory-compute device 112 can include, for example, one or multiple CNM chiplets. The chiplets can be communicatively coupled using CTCPI for high bandwidth and low latency.
In the example of
In an example, the first NOC 118 can comprise a folded Clos topology, such as within each instance of a memory-compute device or as a mesh that couples multiple memory-compute devices in a node. The Clos topology, such as can use multiple, smaller radix crossbars to provide functionality associated with a higher radix crossbar topology, offers various benefits. For example, the Clos topology can exhibit consistent latency and bisection bandwidth across the NOC.
The first NOC 118 can include various distinct switch types including hub switches, edge switches, and endpoint switches. Each of the switches can be constructed as crossbars that provide substantially uniform latency and bandwidth between input and output nodes. In an example, the endpoint switches and the edge switches can include two separate crossbars, one for traffic headed to the hub switches, and the other for traffic headed away from the hub switches. The hub switches can be constructed as a single crossbar that switches all inputs to all outputs.
In an example, the hub switches can have multiple ports each (e.g., four or six ports each), such as depending on whether the particular hub switch participates in inter-chip communications. A number of hub switches that participate in inter-chip communications can be set by an inter-chip bandwidth requirement.
The first NOC 118 can support various payloads (e.g., from 8 to 64-byte payloads; other payload sizes can similarly be used) between compute elements and memory. In an example, the first NOC 118 can be optimized for relatively smaller payloads (e.g., 8-16 bytes) to efficiently handle access to sparse data structures.
In an example, the first NOC 118 can be coupled to an external host via a first physical-layer interface 114, a PCIe subordinate module 116 or endpoint, and a PCIe principal module 126 or root port. That is, the first physical-layer interface 114 can include an interface to allow an external host processor to be coupled to the first memory-compute device 112. An external host processor can optionally be coupled to one or multiple different memory-compute devices, such as using a PCIe switch or other, native protocol switch. Communication with the external host processor through a PCIe-based switch can limit device-to-device communication to that supported by the switch. Communication through a memory-compute device-native protocol switch such as using CTCPI, in contrast, can allow for more full communication between or among different memory-compute devices, including support for a partitioned global address space, such as for creating threads of work and sending events.
In an example, the CTCPI protocol can be used by the first NOC 118 in the first memory-compute device 112, and the first switch 110 can include a CTCPI switch. The CTCPI switch can allow CTCPI packets to be transferred from a source memory-compute device, such as the first memory-compute device 112, to a different, destination memory-compute device (e.g., on the same or other node), such as without being converted to another packet format.
In an example, the first memory-compute device 112 can include an internal host processor 122. The internal host processor 122 can be configured to communicate with the first NOC 118 or other components or modules of the first memory-compute device 112, for example, using the internal PCIe principal module 126, which can help eliminate a physical layer that would consume time and energy. In an example, the internal host processor 122 can be based on a RISC-V ISA processor, and can use the first physical-layer interface 114 to communicate outside of the first memory-compute device 112, such as to other storage, networking, or other peripherals to the first memory-compute device 112. The internal host processor 122 can control the first memory-compute device 112 and can act as a proxy for operating system-related functionality. The internal host processor 122 can include a relatively small number of processing cores (e.g., 2-4 cores) and a host memory device 124 (e.g., comprising a dynamic random access memory (DRAM) module).
In an example, the internal host processor 122 can include PCI root ports. When the internal host processor 122 is in use, then one of its root ports can be connected to the PCIe subordinate module 116. Another of the root ports of the internal host processor 122 can be connected to the first physical-layer interface 114, such as to provide communication with external PCI peripherals. When the internal host processor 122 is disabled, then the PCIe subordinate module 116 can be coupled to the first physical-layer interface 114 to allow an external host processor to communicate with the first NOC 118. In an example of a system with multiple memory-compute devices, the first memory-compute device 112 can be configured to act as a system host or controller. In this example, the internal host processor 122 can be in use, and other instances of internal host processors in the respective other memory-compute devices can be disabled.
The internal host processor 122 can be configured at power-up of the first memory-compute device 112, such as to allow the host to initialize. In an example, the internal host processor 122 and its associated data paths (e.g., including the first physical-layer interface 114, the PCIe subordinate module 116, etc.) can be configured from input pins to the first memory-compute device 112. One or more of the pins can be used to enable or disable the internal host processor 122 and configure the PCI (or other) data paths accordingly.
In an example, the first NOC 118 can be coupled to the scale fabric 106 via a scale fabric interface module 136 and a second physical-layer interface 138. The scale fabric interface module 136, or SIF, can facilitate communication between the first memory-compute device 112 and a device space, such as a PGAS. The PGAS can be configured such that a particular memory-compute device, such as the first memory-compute device 112, can access memory or other resources on a different memory-compute device (e.g., on the same or different node), such as using a load/store paradigm. Various scalable fabric technologies can be used, including CTCPI. CPI, Gen-Z, PCI, or Ethernet bridged over CXL. The scale fabric 106 can be configured to support various packet formats. In an example, the scale fabric 106 supports orderless packet communications or supports ordered packets such as can use a path identifier to spread bandwidth across multiple equivalent paths. The scale fabric 106 can generally support remote operations such as remote memory read, write, and other built-in atomics, remote memory atomics, remote memory-compute device send events, and remote memory-compute device call and return operations.
In an example, the first NOC 118 can be coupled to one or multiple different memory modules, such as including a first memory device 128. The first memory device 128 can include various kinds of memory devices (for example, low-power double data rate 5 (LPDDR5) synchronous DRAM (SDRAM) or graphics double data rate 6 (GDDR6) DRAM, among others). In the example of
The memory module cache can provide storage for frequently accessed memory locations, such as without having to re-access the first memory device 128. In an example, the memory module cache can be configured to cache data only for a particular instance of the memory controller 130. In an example, the memory controller 130 includes a DRAM controller configured to interface with the first memory device 128, such as including DRAM devices. The memory controller 130 can provide access scheduling and bit error management, among other functions.
In an example, the first NOC 118 can be coupled to a hybrid threading processor (HTP 140), a hybrid threading fabric (HTF 142), and a host interface and dispatch module (HIF 120). The HIF 120 can be configured to facilitate access to host-based command request queues and response queues. In an example, the HIF 120 can dispatch new threads of execution on processor or compute elements of the HTP 140 or the HTF 142. In an example, the HIF 120 can be configured to maintain workload balance across the HTP 140 module and the HTF 142 module.
The hybrid threading processor, or HTP 140, can include an accelerator, such as can be based on a RISC-V instruction set. The HTP 140 can include a highly threaded, event-driven processor in which threads can be executed in single instruction rotation, such as to maintain high instruction throughput. The HTP 140 comprises relatively few custom instructions to support low-overhead threading capabilities, event send/receive, and shared memory atomic operators.
The hybrid threading fabric, or HTF 142, can include an accelerator, such as can include a non-von Neumann, coarse-grained, reconfigurable processor. The HTF 142 can be optimized for high-level language operations and data types (e.g., integer or floating point). In an example, the HTF 142 can support data flow computing. The HTF 142 can be configured to use substantially all of the memory bandwidth available on the first memory-compute device 112, such as when executing memory-bound compute kernels.
The HTP and HTF accelerators of the CNM system 102 can be programmed using various high-level, structured programming languages. For example, the HTP and HTF accelerators can be programmed using C/C++, such as using the LLVM compiler framework. The HTP accelerator can leverage an open source compiler environment, such as with various added custom instruction sets configured to improve memory access efficiency, provide a message passing mechanism, and manage events, among other things. In an example, the HTF accelerator can be designed to enable programming of the HTF 142 using a high-level programming language, and the compiler can generate a simulator configuration file or a binary file that runs on the HTF 142 hardware. The HTF 142 can provide a mid-level language for expressing algorithms precisely and concisely, while hiding configuration details of the HTF accelerator itself. In an example, the HTF accelerator tool chain can use an LLVM front-end compiler and the LLVM intermediate representation (IR) to interface with an HTF accelerator back end.
In the example of
The local cache module 212, such as can include an SRAM cache, can be provided to help reduce latency for repetitively-accessed memory locations. In an example, the local cache module 212 can provide a read buffer for sub-memory line accesses. The local cache module 212 can be particularly beneficial for compute elements that have relatively small or no data caches. In some example embodiments, the local cache module 212 is a 2 kilobyte read-only cache.
The memory control module 210, such as can include a DRAM controller, can provide low-level request buffering and scheduling, such as to provide efficient access to the memory device 204, such as can include a DRAM device. In an example, the memory device 204 can include or use a GDDR6 DRAM device, such as having 16 Gb density and 64 Gb/sec peak bandwidth. Other devices can similarly be used.
In an example, the programmable atomic unit 208 can comprise single-cycle or multiple-cycle operators such as can be configured to perform integer addition or more complicated multiple-instruction operations such as bloom filter insert. In an example, the programmable atomic unit 208 can be configured to perform load and store-to-memory operations. The programmable atomic unit 208 can be configured to leverage the RISC-V ISA with a set of specialized instructions to facilitate interactions with the controller 202 to atomically perform user-defined operations.
Programmable atomic requests, such as received from an on-node or off-node host, can be routed to the programmable atomic unit 208 via the second NOC 206 and the controller 202. In an example, custom atomic operations (e.g., carried out by the programmable atomic unit 208) can be identical to built-in atomic operations (e.g., carried out by the built-in atomics module 214) except that a programmable atomic operation can be defined or programmed by the user rather than the system architect. In an example, programmable atomic request packets can be sent through the second NOC 206 to the controller 202, and the controller 202 can identify the request as a custom atomic operation. The controller 202 can then forward the identified request to the programmable atomic unit 208.
In an example, the PAU core 306 is a pipelined processor such that multiple stages of different instructions are executed together per clock cycle. The PAU core 306 can include a barrel-multithreaded processor, with thread control 304 circuitry to switch between different register files (e.g., sets of registers containing current processing state) upon each clock cycle. This enables efficient context switching between currently executing threads. In an example, the PAU core 306 supports eight threads, resulting in eight register files. In an example, some or all of the register files are not integrated into the PAU core 306, but rather reside in a local data cache 310 or the instruction SRAM 308. This reduces circuit complexity in the PAU core 306 by eliminating the traditional flip-flops used for registers in such memories.
The local PAU memory can include instruction SRAM 308, such as can include instructions for various atomics. The instructions comprise sets of instructions to support various application-loaded atomic operators. When an atomic operator is requested, such as by an application chiplet, a set of instructions corresponding to the atomic operator are executed by the PAU core 306. In an example, the instruction SRAM 308 can be partitioned to establish the sets of instructions. In this example, the specific programmable atomic operator being requested by a requesting process can identify the programmable atomic operator by the partition number. The partition number can be established when the programmable atomic operator is registered with (e.g., loaded onto) the programmable atomic unit 302. Other metadata for the programmable instructions can be stored in memory (e.g., in partition tables) local to the programmable atomic unit 302.
In an example, atomic operators manipulate the data cache 310, which is generally synchronized (e.g., flushed) when a thread for an atomic operator completes. Thus, aside from initial loading from the external memory, such as from the memory controller 314, latency can be reduced for most memory operations during execution of a programmable atomic operator thread.
A pipelined processor, such as the PAU core 306, can experience an issue when an executing thread attempts to issue a memory request if an underlying hazard condition would prevent such a request. Here, the memory request is to retrieve data from the memory controller 314, whether it be from a cache on the memory controller 314 or off-die memory. To resolve this issue, the PAU core 306 is configured to deny the memory request for a thread. Generally, the PAU core 306 or the thread control 304 can include circuitry to enable one or more thread rescheduling points in the pipeline. Here, the denial occurs at a point in the pipeline that is beyond (e.g., after) these thread rescheduling points. In an example, the hazard occurred beyond the rescheduling point. Here, a preceding instruction in the thread created the hazard after the memory request instruction passed the last thread rescheduling point prior to the pipeline stage in which the memory request could be made.
In an example, to deny the memory request, the PAU core 306 is configured to determine (e.g., detect) that there is a hazard on memory indicated in the memory request. Here, hazard denotes any condition such that allowing (e.g., performing) the memory request will result in an inconsistent state for the thread. In an example, the hazard is an in-flight memory request. Here, whether or not the data cache 310 includes data for the requested memory address, the presence of the in-flight memory request makes it uncertain what the data in the data cache 310 at that address should be. Thus, the thread must wait for the in-flight memory request to be completed to operate on current data. The hazard is cleared when the memory request completes.
In an example, the hazard is a dirty cache line in the data cache 310 for the requested memory address. Although the dirty cache line generally indicates that the data in the cache is current and the memory controller version of this data is not, an issue can arise on thread instructions that do not operate from the cache. An example of such an instruction uses a built-in atomic operator, or other separate hardware block, of the memory controller 314. In the context of a memory controller, the built-in atomic operators can be separate from the programmable atomic unit 302 and do not have access to the data cache 310 or instruction SRAM 308 inside the PAU. If the cache line is dirty, then the built-in atomic operator will not be operating on the most current data until the data cache 310 is flushed to synchronize the cache and the other off-die memories. This same situation could occur with other hardware blocks of the memory controller, such as cryptography block, encoder, and so forth.
In an example, the HTP accelerator 400 includes a module that is based on a RISC-V instruction set, and can include a relatively small number of other or additional custom instructions to support a low-overhead, threading-capable Hybrid Threading (HT) language. The HTP accelerator 400 can include a highly-threaded processor core, the HTP core 402, in which, or with which, threads can be executed in a single instruction rotation, such as to maintain high instruction throughput. In an example, a thread can be paused when it waits for other pending events to complete. This can allow the compute resources to be efficiently used on relevant work instead of polling. In an example, multiple-thread barrier synchronization can use efficient HTP-to-HTP and HTP-to/from-Host messaging, such as can allow thousands of threads to initialize or wake in, for example, tens of clock cycles.
In an example, the dispatch interface 414 can comprise a functional block of the HTP accelerator 400 for handling hardware-based thread management. That is, the dispatch interface 414 can manage dispatch of work to the HTP core 402 or other accelerators. Non-HTP accelerators, however, are generally not able to dispatch work. In an example, work dispatched from a host can use dispatch queues that reside in, e.g., host main memory (e.g., DRAM-based memory). Work dispatched from the HTP accelerator 400, on the other hand, can use dispatch queues that reside in SRAM, such as within the dispatches for the target HTP accelerator 400 within a particular node.
In an example, the HTP core 402 can comprise one or more cores that execute instructions on behalf of threads. That is, the HTP core 402 can include an instruction processing block. The HTP core 402 can further include, or can be coupled to, the thread controller 412. The thread controller 412 can provide thread control and state for each active thread within the HTP core 402. The data cache 406 can include cache for a host processor (e.g., for local and remote memory-compute devices, including for the HTP core 402), and the instruction cache 404 can include cache for use by the HTP core 402. In an example, the data cache 406 can be configured for read and write operations, and the instruction cache 404 can be configured for read only operations.
In an example, the data cache 406 is a small cache provided per hardware thread. The data cache 406 can temporarily store data for use by the owning thread. The data cache 406 can be managed by hardware or software in the HTP accelerator 400. For example, hardware can be configured to automatically allocate or evict lines as needed, as load and store operations are executed by the HTP core 402. Software, such as using RISC-V instructions, can determine which memory accesses should be cached and when lines should be invalidated or written back to other memory locations.
Data caching on the HTP accelerator 400 has various benefits, including making larger accesses more efficient for the memory controller, thereby allowing an executing thread to avoid stalling. However, there are situations when using the cache causes inefficiencies. An example includes accesses where data is accessed only once and causes thrashing of the cache lines. To help address this problem, the HTP accelerator 400 can use a set of custom load instructions to force a load instruction to check for a cache hit and, on a cache miss, to issue a memory request for the requested operand and not put the obtained data in the data cache 406. The HTP accelerator 400 thus includes various different types of load instructions, including non-cached and cache line loads. The non-cached load instructions use the cached data if dirty data is present in the cache. The non-cached load instructions ignore clean data in the cache and do not write accessed data to the data cache. For cache line load instructions, the complete data cache line (e.g., comprising 64 bytes) can be loaded from memory into the data cache 406 and can load the addressed memory into a specified register. These loads can use the cached data if clean or dirty data is in the data cache 406. If the referenced memory location is not in the data cache 406, then the entire cache line can be accessed from memory. Use of the cache line load instructions can reduce cache misses when sequential memory locations are being referenced (such as memory copy operations) but can also waste memory and bandwidth at the NOC interface 416 if the referenced memory data is not used.
In an example, the HTP accelerator 400 includes a custom store instruction that is non-cached. The non-cached store instruction can help avoid thrashing the data cache 406 with write data that is not sequentially written to memory.
In an example, the HTP accelerator 400 further includes a translation block 408. The translation block 408 can include a virtual-to-physical translation block for local memory of a memory-compute device. For example, a host processor, such as in the HTP core 402, can execute a load or store instruction, and the instruction can generate a virtual address. The virtual address can be translated to a physical address of the host processor, such as using a translation table from the translation block 408. The memory interface 410, for example, can include an interface between the HTP core 402 and the NOC interface 416.
In an example, the HTF 500 comprises an HTF cluster 502 that includes multiple HTF tiles, including an example tile 504, or Tile N. Each HTF tile can include one or more compute elements with local memory and arithmetic functions. For example, each tile can include a compute pipeline with support for integer and floating-point operations. In an example, the data path, compute elements, and other infrastructure can be implemented as hardened IP to provide maximum performance while minimizing power consumption and reconfiguration time.
In the example of
The HTF cluster 502 can further include memory interface modules, including a first memory interface module 506. The memory interface modules can couple the HTF cluster 502 to a NOC, such as the first NOC 118 of
In the example of
In an example, the synchronous fabric can exchange messages that include data and control information. The control information can include, among other things, instruction RAM address information or a thread identifier. The control information can be used to set up a data path, and a data message field can be selected as a source for the path. Generally, the control fields can be provided or received earlier, such that they can be used to configure the data path. For example, to help minimize any delay through the synchronous domain pipeline in a tile, the control information can arrive at a tile a few clock cycles before the data field. Various registers can be provided to help coordinate dataflow timing in the pipeline.
In an example, each tile in the HTF cluster 502 can include multiple memories. Each memory can have the same width as the data path (e.g., 512 bits) and can have a specified depth, such as in a range of 512 to 1024 elements. The tile memories can be used to store data that supports data path operations. The stored data can include constants loaded as part of a kernel's cluster configuration, for example, or can include variables calculated as part of the data flow. In an example, the tile memories can be written from the asynchronous fabric as a data transfer from another synchronous domain or can include a result of a load operation such as initiated by another synchronous domain. The tile memory can be read via synchronous data path instruction execution in the synchronous domain.
In an example, each tile in an HTF cluster 502 can have a dedicated instruction RAM (INST RAM). In an example of an HTF cluster 502 with sixteen tiles, and instruction RAM instances with sixty-four entries, the cluster can allow algorithms to be mapped with up to 1024 multiply-shift and/or arithmetic-logic unit (ALU) operations. The various tiles can optionally be pipelined together, such as using the synchronous fabric, to allow data flow compute with minimal memory access, thus minimizing latency and reducing power consumption. In an example, the asynchronous fabric can allow memory references to proceed in parallel with computation, thereby providing more efficient streaming kernels. In an example, the various tiles can include built-in support for loop-based constructs and can support nested looping kernels.
The synchronous fabric can allow multiple tiles to be pipelined, such as without a need for data queuing. Tiles that participate in a synchronous domain can, for example, act as a single pipelined data path. A first or base tile (e.g., Tile N−2, in the example of
In an example, the synchronous domain comprises a set of connected tiles in the HTF cluster 502. Execution of a thread can begin at the domain's base tile and can progress from the base tile, via the synchronous fabric, to other tiles in the same domain. The base tile can provide the instruction to be executed for the first tile. The first tile can, by default, provide the same instruction for the other connected tiles to execute. However, in some examples, the base tile, or a subsequent tile, can conditionally specify or use an alternative instruction. The alternative instruction can be chosen by having the tile's data path produce a Boolean conditional value and then can use the Boolean value to choose between an instruction set of the current tile and the alternate instruction.
The asynchronous fabric can be used to perform operations that occur asynchronously relative to a synchronous domain. Each tile in the HTF cluster 502 can include an interface to the asynchronous fabric. The inbound interface can include, for example, a first-in first-out (FIFO) buffer or queue (e.g., AF IN QUEUE) to provide storage for messages that cannot be immediately processed. Similarly, the outbound interface of the asynchronous fabric can include a FIFO buffer or queue (e.g., AF OUT QUEUE) to provide storage for messages that cannot be immediately sent out.
In an example, messages in the AF can be classified as data messages or control messages. Data messages can include a SIMD width data value that is written to either tile memory 0 (MEM_0) or memory 1 (MEM_1). Control messages can be configured to control thread creation, free resources, or issue external memory references.
A tile in the HTF cluster 502 can perform various compute operations for the HTF. The compute operations can be performed by configuring the data path within the tile. In an example, a tile includes two functional blocks that perform the compute operations for the tile: a Multiply and Shift Operation block (MS OP) and an Arithmetic. Logical, and Bit Operation block (ALB OP). The two blocks can be configured to perform pipelined operations such as a Multiply and Add, or a Shift and Add, among others.
In an example, each instance of a memory-compute device in a system can have a complete supported instruction set for its operator blocks (e.g., MS OP and ALB OP). In this case, binary compatibility can be realized across all devices in the system. However, in some examples, it can be helpful to maintain a base set of functionality and optional instruction set classes, such as to meet various design tradeoffs, such as die size. The approach can be similar to how the RISC-V instruction set has a base set and multiple optional instruction subsets.
In an example, the example tile 504 can include a Spoke RAM. The Spoke RAM can be used to specify which input (e.g., from among the four SF tile inputs and the base tile input) is the primary input for each clock cycle. The Spoke RAM read address input can originate at a counter that counts from zero to Spoke Count minus one. In an example, different spoke counts can be used on different tiles, such as within the same HTF cluster 502, to allow a number of slices, or unique tile instances, used by an inner loop to determine the performance of a particular application or instruction set. In an example, the Spoke RAM can specify when a synchronous input is to be written to a tile memory, for instance when multiple inputs for a particular tile instruction are used and one of the inputs arrives before the others. The early-arriving input can be written to the tile memory and can be later read when all of the inputs are available. In this example, the tile memory can be accessed as a FIFO memory, and FIFO read and write pointers can be stored in a register-based memory region or structure in the tile memory.
The configuration of chiplets as individual modules of a system is distinct from such a system being implemented on single chips that contain distinct device blocks (e.g., IP blocks) on one substrate (e.g., single die), such as a SoC, or multiple discrete packaged devices integrated on a printed circuit board (PCB). In general, chiplets provide better performance (e.g., lower power consumption, reduced latency, etc.) than discrete packaged devices, and chiplets provide greater production benefits than single die chips. These production benefits can include higher yields or reduced development costs and time.
Chiplet systems can include, for example, one or more application (or processor) chiplets and one or more support chiplets. Here, the distinction between application and support chiplets is simply a reference to the likely design scenarios for the chiplet system. Thus, for example, a synthetic vision chiplet system can include, by way of example only, an application chiplet to produce the synthetic vision output along with support chiplets, such as a memory controller chiplet, a sensor interface chiplet, or a communication chiplet. In a typical use case, the synthetic vision designer can design the application chiplet and source the support chiplets from other parties. Thus, the design expenditure (e.g., in terms of time or complexity) is reduced by avoiding the design and production of functionality embodied in the support chiplets.
Chiplets also support the tight integration of IP blocks that can otherwise be difficult, such as those manufactured using different processing technologies or using different feature sizes (or utilizing different contact technologies or spacings). Thus, multiple ICs or IC assemblies, with different physical, electrical, or communication characteristics can be assembled in a modular manner to provide an assembly with various desired functionalities. Chiplet systems can also facilitate adaptation to suit the needs of different larger systems into which the chiplet system will be incorporated. In an example, ICs or other assemblies can be optimized for the power, speed, or heat generation for a specific function—as can happen with sensors—can be integrated with other devices more easily than attempting to do so on a single die. Additionally, by reducing the overall size of the die, the yield for chiplets tends to be higher than that of more complex, single die devices.
The application chiplet 610 is illustrated as including a chiplet system NOC 620 to support a chiplet network 622 for inter-chiplet communications. In example embodiments, the chiplet system NOC 620 can be included on the application chiplet 610. In an example, the first NOC 118 from the example of
In an example, the chiplet system 602 can include or comprise a portion of the first memory-compute node 104 or the first memory-compute device 112. That is, the various blocks or components of the first memory-compute device 112 can include chiplets that can be mounted on the peripheral board 604, the package substrate 606, and the interposer 608. The interface components of the first memory-compute device 112 can comprise, generally, the host interface chiplet 612. The memory and memory control-related components of the first memory-compute device 112 can comprise, generally, the memory controller chiplet 614. The various accelerator and processor components of the first memory-compute device 112 can comprise, generally, the application chiplet 610 or instances thereof, and so on.
The CPI interface, such as can be used for communication between or among chiplets in a system, is a packet-based network that supports virtual channels to enable a flexible and high-speed interaction between chiplets. CPI enables bridging from intra-chiplet networks to the chiplet network 622. For example, AXI is a widely used specification to design intra-chip communications. AXI specifications, however, cover a great variety of physical design options, such as the number of physical channels, signal timing, power, and so forth. Within a single chip, these options are generally selected to meet design goals, such as power consumption, speed, and so forth. However, to achieve the flexibility of the chiplet system, an adapter, such as CPI, is used to interface between the various AXI design options that can be implemented in the various chiplets. By enabling a physical channel to virtual channel mapping and encapsulating time-based signaling with a packetized protocol, CPI bridges intra-chiplet networks across the chiplet network 622.
CPI can use a variety of different physical layers to transmit packets. The physical layer can include simple conductive connections, drivers to increase the voltage, or otherwise facilitate transmitting the signals over longer distances. An example of one such a physical layer can include the Advanced Interface Bus (AIB), which, in various examples, can be implemented in the interposer 608. An AIB transmits and receives data using source synchronous data transfers with a forwarded clock. Packets are transferred across the AIB at single data rate (SDR) or dual data rate (DDR) with respect to the transmitted clock. Various channel widths are supported by AIB. The channel can be configured to have a symmetrical number of transmit (TX) and receive (RX) input/outputs (I/Os) or have a non-symmetrical number of transmitters and receivers (e.g., either all transmitters or all receivers). The channel can act as an AIB principal or subordinate depending on which chiplet provides the principal clock. AIB I/O cells support three clocking modes: asynchronous (i.e., non-clocked), SDR, and DDR. In various examples, the non-clocked mode is used for clocks and some control signals. The SDR mode can use dedicated SDR only I/O cells or dual use SDR/DDR I/O cells.
In an example, CPI packet protocols (e.g., point-to-point or routable) can use symmetrical receive and transmit I/O cells within an AIB channel. The CPI streaming protocol allows more flexible use of the AIB 1/O cells. In an example, an AIB channel for streaming mode can configure the I/O cells as all TX, all RX, or half TX and half RX. CPI packet protocols can use an AIB channel in either SDR or DDR operation mode. In an example, the AIB channel is configured in increments of 80 I/O cells (i.e., 40 TX and 40 RX) for SDR mode and 40 I/O cells for DDR mode. The CPI streaming protocol can use an AIB channel in either SDR or DDR operation modes. Here, in an example, the AIB channel is in increments of 40 I/O cells for both SDR and DDR modes. In an example, each AIR channel is assigned a unique interface identifier. The identifier is used during CPI reset and initialization to determine paired AIB channels across adjacent chiplets. In an example, the interface identifier is a 20-bit value comprising a seven-bit chiplet identifier, a seven-bit column identifier, and a six-bit link identifier. The AIB physical layer transmits the interface identifier using an AIB out-of-band shift register. The 20-bit interface identifier is transferred in both directions across an AIB interface using bits 32-51 of the shift registers.
AIB defines a stacked set of AIB channels as an AIB channel column. An AIB channel column has some number of AIB channels plus an auxiliary channel. The auxiliary channel contains signals used for AIB initialization. All AIB channels (other than the auxiliary channel) within a column are of the same configuration (e.g., all TX, all RX, or half TX and half RX), as well as having the same number of data I/O signals. In an example, AIR channels are numbered in continuous increasing order starting with the AIB channel adjacent to the AUX channel. The AIB channel adjacent to the AUX is defined to be AIB channel zero.
Generally, CPI interfaces on individual chiplets can include serialization-deserialization (SERDES) hardware. SERDES interconnects work well for scenarios in which high-speed signaling with low signal count is desirable. SERDES, however, can result in additional power consumption and longer latencies for multiplexing and demultiplexing, error detection or correction (e.g., using block level cyclic redundancy checking (CRC)), link-level retry, or forward error correction. However, when low latency or energy consumption is a primary concern for ultra-short reach, chiplet-to-chiplet interconnects, a parallel interface with clock rates that allow data transfer with minimal latency can be utilized. CPI includes elements to minimize both latency and energy consumption in these ultra-short reach chiplet interconnects.
For flow control, CPI employs a credit-based technique. A recipient, such as the application chiplet 610, provides a sender, such as the memory controller chiplet 614, with credits that represent available buffers. In an example, a CPI recipient includes a buffer for each virtual channel for a given time-unit of transmission. Thus, if the CPI recipient supports five messages in time and a single virtual channel, the recipient has five buffers arranged in five rows (e.g., one row for each unit time). If four virtual channels are supported, then the recipient has twenty buffers arranged in five rows. Each buffer holds the payload of one CPI packet.
When the sender transmits to the recipient, the sender decrements the available credits based on the transmission. Once all credits for the recipient are consumed, the sender stops sending packets to the recipient. This ensures that the recipient always has an available buffer to store the transmission.
As the recipient processes received packets and frees buffers, the recipient communicates the available buffer space back to the sender. This credit return can then be used by the sender to allow transmitting of additional information.
The example of
Additionally, dedicated device interfaces, such as one or more industry standard memory interfaces (such as, for example, synchronous memory interfaces, such as DDR5, DDR6), can be used to connect a device to a chiplet. Connection of a chiplet system or individual chiplets to external devices (such as a larger system) can be through a desired interface (for example, a PCIe interface). Such an external interface can be implemented, in an example, through the host interface chiplet 612, which, in the depicted example, provides a PCIe interface external to the chiplet system. Such dedicated chiplet interfaces 626 are generally employed when a convention or standard in the industry has converged on such an interface. The illustrated example of a DDR interface connecting the memory controller chiplet 614 to a DRAM memory device chiplet 616 is just such an industry convention.
Of the variety of possible support chiplets, the memory controller chiplet 614 is likely present in the chiplet system due to the near omnipresent use of storage for computer processing as well as sophisticated state-of-the-art for memory devices. Thus, using memory device chiplets 616 and memory controller chiplets 614 produced by others gives chiplet system designers access to robust products by sophisticated producers. Generally, the memory controller chiplet 614 provides a memory device-specific interface to read, write, or erase data. Often, the memory controller chiplet 614 can provide additional features, such as error detection, error correction, maintenance operations, or atomic operator execution. For some types of memory, maintenance operations tend to be specific to the memory device chiplet 616, such as garbage collection in NAND flash or storage class memories and temperature adjustments (e.g., cross temperature management) in NAND flash memories. In an example, the maintenance operations can include logical-to-physical (L2P) mapping or management to provide a level of indirection between the physical and logical representation of data. In other types of memory, for example DRAM, some memory operations, such as refresh, can be controlled by a host processor or a memory controller at some times, and at other times, controlled by the DRAM memory device, or by logic associated with one or more DRAM devices, such as an interface chip (in an example, a buffer).
Atomic operators are a data manipulation that, for example, can be performed by the memory controller chiplet 614. In other chiplet systems, the atomic operators can be performed by other chiplets. For example, an atomic operator of “increment” can be specified in a command by the application chiplet 610, the command including a memory address and possibly an increment value. Upon receiving the command, the memory controller chiplet 614 retrieves a number from the specified memory address, increments the number by the amount specified in the command, and stores the result. Upon a successful completion, the memory controller chiplet 614 provides an indication of the command success to the application chiplet 610. Atomic operators avoid transmitting the data across the chiplet mesh network 624, resulting in lower latency execution of such commands.
Atomic operators can be classified as built-in atomics or programmable (e.g., custom) atomics. Built-in atomics are a finite set of operations that are immutably implemented in hardware. Programmable atomics are small programs that can execute on a PAU (e.g., a custom atomic unit (CAU)) of the memory controller chiplet 614.
The memory device chiplet 616 can be, or include any combination of, volatile memory devices or non-volatile memories. Examples of volatile memory devices include, but are not limited to, RAM, such as DRAM, synchronous DRAM (SDRAM), and GDDR6 SDRAM, among others. Examples of non-volatile memory devices include, but are not limited to, NAND-type flash memory and storage class memory (e.g., phase-change memory or memristor based technologies, ferroelectric RAM (FeRAM), among others. The illustrated example includes the memory device chiplet 616 as a chiplet; however, the device can reside elsewhere, such as in a different package on the peripheral board 604. For many applications, multiple memory device chiplets can be provided. In an example, these memory device chiplets can each implement one or multiple storage technologies and may include integrated compute hosts. In an example, a memory chiplet can include multiple stacked memory die of different technologies (for example, one or more SRAM devices stacked or otherwise in communication with one or more DRAM devices). In an example, the memory controller chiplet 614 can serve to coordinate operations between multiple memory chiplets in the chiplet system 602 (for example, to use one or more memory chiplets in one or more levels of cache storage and to use one or more additional memory chiplets as main memory). The chiplet system 602 can include multiple memory controller chiplet 614 instances, as can be used to provide memory control functionality for separate hosts, processors, sensors, networks, and so forth. A chiplet architecture, such as in the illustrated system, offers advantages in allowing adaptation to different memory storage technologies and different memory interfaces, through updated chiplet configurations, such as without requiring redesign of the remainder of the system structure.
The example of
In the example of
The first chiplet 702 can further include one or multiple memory controllers 716. The memory controllers 716 can correspond to respective different NOC endpoint switches interfaced with the first NOC hub edge 714. In an example, the memory controller 716 comprises the memory controller chiplet 614, the memory controller 130, the memory subsystem 200, or other memory-compute implementation. The memory controllers 716 can be coupled to respective different memory devices, for example, including a first external memory module 712a or a second external memory module 712b. The external memory modules can include, e.g., GDDR6 memories that can be selectively accessed by the respective different chiplets in the system.
The first chiplet 702 can further include a first HTP chiplet 718 and second HTP chiplet 720, such as coupled to the first NOC hub edge 714 via respective different NOC endpoint switches. The HTP chiplets can correspond to HTP accelerators, such as the HTP 140 from the example of
The CNM NOC hub 710 can be coupled to NOC hub instances in other chiplets or other CNM packages by way of various interfaces and switches. For example, the CNM NOC hub 710 can be coupled to a CPI interface by way of multiple different NOC endpoints on the first CNM package 700. Each of the multiple different NOC endpoints can be coupled, for example, to a different node outside of the first CNM package 700. In an example, the CNM NOC hub 710 can be coupled to other peripherals, nodes, or devices using CTCPI or other, non-CPI protocols. For example, the first CNM package 700 can include a PCIe scale fabric interface (PCIE/SFI) or a CXL interface configured to interface the first CNM package 700 with other devices. In an example, devices to which the first CNM package 700 is coupled using the various CPI, PCIe, CXL, or other fabric, can make up a common global address space.
In the example of
The tiled chiplet example 800 includes, as one or multiple of its CNM clusters, instances of the first CNM package 700 from the example of
In the example of
In an example, one of the CNM chiplets in the tiled chiplet example 800 can include a host interface (e.g., corresponding to the host interface 724 from the example of
The commands 1010-1050 are the same except for differences in bits 27-31. The value in bits 27-31 indicates which hybrid threaded accelerator (HTA) of the HTP 140 will execute the child thread. Command 1010 targets HTA0, command 1020 targets HTA1, command 1030 targets HTA2, and command 1040 targets HTA3. Instead of the HTA being on the HTP 140, it may be on the HTF 142. For example, commands 1010-1020 may target HTAs of the HTP 140 and commands 1030-1040 may target HTAs of the HTF 142.
The command 1050 is a busy-fail variant of the command 1010. Busy-fail variants of the commands 1020-1040 are also contemplated. If a device does not support busy-fail, the busy-fail variant may be treated as the corresponding non-busy-fail version. If a thread creation request for the non-busy-fail commands 1010-1040 cannot immediately be serviced (e.g., because insufficient memory is available to allocate space for the return values of the child thread), the parent thread is paused until the child thread can be created. If a thread creation request for a busy-fail command cannot immediately be serviced, a failing status is returned from the command.
The two-bit CC parameter indicates the number of call arguments (0, 1, 2, or 4). Up to four data values can be passed to the target routine as starting values. The call argument count is provided by the CC instruction field (specified in assembly by suffixes C0, C1, C2 or C4). In some example embodiments, the actual argument values are obtained from X registers a3-a6 of the parent thread.
The two-bit RC parameter indicates the number of return arguments (no return, 0, 1, or 2). An HTP can only create a thread on an accelerator resource if the calling HTP has space to hold the return information. The return information includes both the caller ID and up to two 64-bit return values. The fiber create instruction specifies the storage space required for the return information. The return information suffix options are NR, R0, R1, and R2. The NR suffix implies that no return information is to be stored (i.e., the join instruction will not provide any information). The R0 suffix implies that the caller ID will be available for a join instruction. The R1 and R2 suffixes imply that either one or two 64-bit return arguments in addition to the caller ID will be stored and available for a join instruction.
The return information storage is allocated when the fiber create instruction is executed. If insufficient return information space is available, then the fiber create instruction is paused until space becomes available. Fiber create instructions with the NR suffix require no return information storage and the number outstanding is limited to the size of a counter to track the number outstanding. The R0 suffix requires storage for the caller ID but no return values, and the R1 and R2 require both caller ID and return value space. The more information a set of created fibers requires results in smaller maximum outstanding fibers.
If cleared, the one-bit NF field instructs the HTA to flush all dirty data from the executing thread's data cache. If the NF field is set, then the dirty data is not flushed but left in the data cache.
The return information storage is allocated when the fiber create instruction is executed. If insufficient return information space is available, then the fiber create instruction is paused until space becomes available. Fiber create instructions with the NR suffix require no return information storage and the number outstanding is limited to the size of a counter to track the number outstanding. The R0 suffix requires storage for the caller ID but no return values, and the R1 and R2 require both caller ID and return value space. The more information a set of created fibers requires results in smaller maximum outstanding fibers.
In addition to the data within the commands 1010-1050 themselves, additional fields may be stored in the X registers of the parent thread. For example, X register a0 may indicate the target of the command. The target input provides accelerator specific information to determine where to start the created thread. For an HTP resource, the target is a virtual address and is used to decide which device to start the thread on. The fiber create (EFC) instruction looks at the value in a0, interprets it as an address, and decides if it is a local or remote address. Local addresses target a local node HTP or HTF, and remote addresses target the specific remote node indicated by the address. Note that only the bits of the address that indicate local or remote and which remote node are used by the instruction. For all other resources, the target value is sent to the dispatcher associated with the resource. Each resource dispatcher uses the target value as appropriate for the specific resource being dispatched. For an HTF resource, if the target value is a private address, then an HTF resource is started within the chiplet referenced by the private address.
The function address is, in some example embodiments, accessed from X register a1 of the parent thread. For HTP, execution begins at the address in register a1. For HTF, a1 specifies the kernel that is to be loaded/executed. Other accelerator types will use the function address as appropriate.
X register a2 may store a caller identifier. For example, a 16-bit caller ID may be provided in register a2. The caller ID is sent to the accelerator resource and echoed back in the return. The caller ID is only used by the caller to match a return to a specific call. The accelerator resource does not use the caller ID value.
Assembly instructions for the commands 1010-1050 may be constructed using the prefix EFC and appending additional information to indicate the variant of the desired command. Example assembly instructions include EFC.HTA0, EFC.HTA1, EFC.HTA2, EFC.HTA3, EFC.HTA0.BF, ETC.HTF, ETC.HTP.C4.NR, EFC.HTP.C2.R1, and EFC.HTP.BF.C2.R1. For example, the suffixes .C0-.C4 may indicate the value to be encoded in the CC field of the commands 1010-1050. As another example, the suffixes .R0-.R2 may indicate the number of return values, with the suffix .NR indicating No Return. Thus, these four suffixes indicate the value to be encoded in the RC field of the commands 1010-1050. As still another example, the suffix .NF may indicate that the NF bit should be set; assembly instructions lacking the .NF suffix may use a default value of having the NF bit cleared.
In some example embodiments, master threads (i.e., thread created by a host) may execute any of the defined EFC instructions, but HTP fiber threads (i.e., thread create by an HTP) are not permitted to execute a non-busy fail HTP fiber create. In these embodiments, a trap will result if a fiber attempts to execute a non-busy fail HTP fiber create.
Commands 1110 and 1130 are wait versions of the EFJ and EFJA commands. Commands 1120 and 1140 are non-wait versions of the EFJ and EFJA commands. The wait variant of the EFJ command will pause thread execution until a fiber has returned. The join non-wait does not pause thread execution but rather provides a success/failure status. Note that the EFJ instruction only joins fibers created with .R0, .R1 and .R2 suffixes. Fibers created by .NR are not visible to the EFJ instruction.
In some example embodiments, the assembly instructions for the commands 1120 and 1140 include a .NW suffix to indicate that they are the non-wait version of the commands.
The wait variant of the EFJA command waits for all fibers created by the executing thread to return and provides the number of fibers that are being joined. The non-wait variant does not wait, but rather returns the number of fibers that have returned but not been joined. The EFJA instructions write to register a0 either the number of fibers being joined or, for an EFJA.NW, a value of −1 indicating no threads were ready to join. Note that only fibers created with suffixes .R0, .R1, or .R2 are included in the returned fiber count. Fibers created with .NR are not included in the returned fiber count, but the wait variant of the EFJA instruction will pause until all fibers, including those created with .NR, have completed.
The EFJ and EFJA commands 1110-1140 can optionally invalidate all clean data from the executing thread's data cache. The clean data is invalidated if the NI field is set. Note that dirty data is not flushed or invalidated.
The ETR command 1150 passes arguments back to the parent thread that initiated the current thread (through a host thread create or HTP fiber create). Once the thread has completed the return instruction, the thread is terminated. The RC2 value of the ETR command 1150 is set to the same value as the RC value of the command 1010-1050 that created the child thread. Thus, the RC2 value indicates the count of return values (e.g., NR, 0, 1, or 2 return values).
In some example embodiments, up to two data values can be passed to the parent thread. The return argument count is provided by the RC2 instruction field (specified in assembly by suffixes R0, R1, R2, or no suffix). When suffixes R0, R1, or R2 are specified, then the number of arguments specified by the ETR instruction will be checked against the number of return arguments specified by the EFC instruction that originally created the thread, and the return arguments are obtained from X registers RS1 and RS2. For example, when 5-bit values are used for RS1 and RS2, the values may be used as indices to identify one of 32 registers in which the return values may be stored. When no suffix is specified, then the RC2 field has the value 3, no argument count checking is performed, and the return arguments are obtained from a0 and a1. Thus, the return values may be found either in predefined registers (a0 and a1, in this example), in registers defined in the command (indicated by RS1 and RS2, in this example), memory defined in the command or in registers (e.g., by using RS1 and/or RS2 as a memory address, by using data stored in the register indicate by RS1 and/or RS2 as a memory address, or any suitable combination thereof (e.g., using one value as a page address and another value as an offset within the page)). As still another option, the return values may be found as embedded data in the command itself (e.g., by using a 64-bit version of the ETR command that includes space for up to two 32-bit return values).
After the join is complete, a register (e.g., register a0) may provide the success/failure status or the caller ID provided to the EFC instruction. If a join is executed and the child thread is available and was created with .R0, .R1, or .R2, the register stores the caller ID of the thread. If no child thread is available but at least one child thread is active, the thread waits on an EFJ and returns −1 in the register for an EFJ.NW. If no child thread is available and no child threads are active, a trap is generated for the illegal join. The return values may be copied into other registers of the parent thread (e.g., register a1 if a single value is returned, registers a1-a2 if two values are returned, and so on).
In operation 1210, the HTP 140 receives a thread create instruction (e.g., an ETC instruction) from a parent thread that indicates a number of return parameters to be generated by a child thread created by the thread create instruction. For example,
The HTP 140, in operation 1220, reserves, based on the number of return parameters, space in a memory to store the return parameters. For example, if each return parameter is 64 bits in size, one 64-bit memory block is reserved for each return parameter. Thus, continuing with the example commands of
The HTP 140 creates the child thread based at least in part on the reserving of the space in the memory to store the return parameters (operation 1230). Thus, after operation 1230, both the parent thread and the child thread are executing on the HTP 140 (as shown in
The HTP 140 may receive a thread return instruction from the child thread. For example, the instruction 1150 of
In operation 1240, the HTP 140 provides access to the return parameters from the reserved space to the parent thread based at least in part on the thread return instruction from the child thread. Access to the return parameters may be provided by copying the return parameters from the reserved space into the register space of the parent thread. In some example embodiments, operation 1240 is performed after both the thread return instruction from the child thread is received and a thread join instruction is received from the parent thread. For example, one of the commands 1110-1140 of
For example, when the thread return command 1150 is executed by a child thread, a RAB may be allocated in the memory device 128 or on the HTP 140 itself. The return values are copied from the registers indicated in the thread return command 1150 to the return arguments of the RAB. When multiple child threads return before the parent thread executes a join command, they are stored as a linked list, so the RAB head pointer 1320 of the parent thread points to the first RAB structure 1330, the RAB next pointer of the first RAB structure points to a second RAB structure 1340, and so on. When the join instruction is executed, the parent thread gains access to the linked list of RAB structures and can traverse the list to process the return values. Each RAB structure includes the Caller ID indicated in the thread create function, allowing the parent thread to properly handle the return values for the child thread.
In alternative embodiments, the machine 1400 can operate as a standalone device or can be connected (e.g., networked) to other machines. In a networked deployment, the machine 1400 can operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, the machine 1400 can act as a peer machine in peer-to-peer (P2P) (or other distributed) network environment. The machine 1400 can be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations.
The machine 1400 (e.g., computer system) can include a hardware processor 1402 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 1404, a static memory 1406 (e.g., memory or storage for firmware, microcode, a basic-input-output (BIOS), unified extensible firmware interface (UEFI), etc.), and mass storage device 1408 (e.g., hard drives, tape drives, flash storage, or other block devices) some or all of which can communicate with each other via an interlink 1430 (e.g., bus). The machine 1400 can further include a display device 1410, an alphanumeric input device 1412 (e.g., a keyboard), and a user interface (UI) Navigation device 1414 (e.g., a mouse). In an example, the display device 1410, the input device 1412, and the UI navigation device 1414 can be a touch screen display. The machine 1400 can additionally include a signal generation device 1418 (e.g., a speaker), a network interface device 1420, and one or more sensor(s) 1416, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The machine 1400 can include an output controller 1428, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).
Registers of the hardware processor 1402, the main memory 1404, the static memory 1406, or the mass storage device 1408 can be, or include, a machine-readable media 1422 on which is stored one or more sets of data structures or instructions 1424 (e.g., software) embodying or used by any one or more of the techniques or functions described herein. The instructions 1424 can also reside, completely or at least partially, within any of registers of the hardware processor 1402, the main memory 1404, the static memory 1406, or the mass storage device 1408 during execution thereof by the machine 1400. In an example, one or any combination of the hardware processor 1402, the main memory 1404, the static memory 1406, or the mass storage device 1408 can constitute the machine-readable media 1422. While the machine-readable media 1422 is illustrated as a single medium, the term “machine-readable medium” can include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) configured to store the one or more instructions 1424.
The term “machine readable medium” can include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 1400 and that cause the machine 1400 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting machine-readable medium examples can include solid-state memories, optical media, magnetic media, and signals (e.g., radio frequency signals, other photon-based signals, sound signals, etc.). In an example, a non-transitory machine-readable medium comprises a machine-readable medium with a plurality of particles having invariant (e.g., rest) mass, and thus are compositions of matter. Accordingly, non-transitory machine-readable media are machine readable media that do not include transitory propagating signals. Specific examples of non-transitory machine readable media can include: non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.
In an example, information stored or otherwise provided on the machine-readable media 1422 can be representative of the instructions 1424, such as instructions 1424 themselves or a format from which the instructions 1424 can be derived. This format from which the instructions 1424 can be derived can include source code, encoded instructions (e.g., in compressed or encrypted form), packaged instructions (e.g., split into multiple packages), or the like. The information representative of the instructions 1424 in the machine-readable media 1422 can be processed by processing circuitry into the instructions to implement any of the operations discussed herein. For example, deriving the instructions 1424 from the information (e.g., processing by the processing circuitry) can include: compiling (e.g., from source code, object code, etc.), interpreting, loading, organizing (e.g., dynamically or statically linking), encoding, decoding, encrypting, unencrypting, packaging, unpackaging, or otherwise manipulating the information into the instructions 1424.
In an example, the derivation of the instructions 1424 can include assembly, compilation, or interpretation of the information (e.g., by the processing circuitry) to create the instructions 1424 from some intermediate or preprocessed format provided by the machine-readable media 1422. The information, when provided in multiple parts, can be combined, unpacked, and modified to create the instructions 1424. For example, the information can be in multiple compressed source code packages (or object code, or binary executable code, etc.) on one or several remote servers. The source code packages can be encrypted when in transit over a network and decrypted, uncompressed, assembled (e.g., linked) if necessary, compiled or interpreted (e.g., into a library, stand-alone executable etc.) at a local machine, and executed by the local machine.
The instructions 1424 can be further transmitted or received over a communications network 1426 using a transmission medium via the network interface device 1420 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol, transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks can include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), plain old telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, peer-to-peer (P2P) networks, among others. In an example, the network interface device 1420 can include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the network 1426. In an example, the network interface device 1420 can include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the machine 1400, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software. A transmission medium is a machine readable medium.
To better illustrate the methods and apparatuses described herein, a non-limiting set of Example embodiments are set forth below as numerically identified Examples.
Example 1 is an apparatus comprising: a memory interface coupled to a memory; a data cache; an instruction cache; and a processing element configured to: access data from the data cache; and execute instructions from the instruction cache to perform operations comprising: receiving a thread create instruction from a parent thread executing on the processing element, the thread create instruction indicating a number of return parameters to be generated by a child thread created by the thread create instruction; reserving, via the memory interface and based on the number of return parameters, space in the memory to store the return parameters; creating the child thread based at least in part on the reserving of the space in the memory; and providing access to the return parameters from the reserved space to the parent thread based at least in part on a thread return instruction from the child thread.
In Example 2, the subject matter of Example 1 includes, wherein: the operations further comprise receiving a join instruction from the parent thread; and the providing of the access to the return parameters from the reserved space to the parent thread is in response to the receipt of the join instruction.
In Example 3, the subject matter of Example 2 includes, wherein: the thread create instruction further indicates a caller identifier; and the caller identifier is provided to the parent thread in response to the receipt of the join instruction.
In Example 4, the subject matter of Examples 1-3 includes, wherein the thread create instruction from the parent thread that indicates the number of return parameters uses two bits to indicate the number of return parameters.
In Example 5, the subject matter of Examples 1-4 includes, bits for each return parameter.
In Example 6, the subject matter of Examples 1-5 includes, wherein the providing of the access to the return parameters from the reserved space to the parent thread comprises copying data from the reserved space to a register state of the parent thread.
In Example 7, the subject matter of Examples 1-6 includes, wherein the operations further comprise: in response to the thread return instruction, checking that all operations initiated by the child thread have either completed or been acknowledged.
In Example 8, the subject matter of Examples 1-7 includes, wherein the operations further comprise: waiting for all threads created by the child thread to complete before sending the thread return instruction from the child thread.
In Example 9, the subject matter of Examples 1-8 includes, wherein the thread create instruction further indicates whether to start the child thread on a local node or a remote node.
In Example 10, the subject matter of Examples 1-9 includes, wherein the creating of the child thread comprises: beginning execution of the child thread from an address read from a register of the parent thread.
In Example 11, the subject matter of Examples 1-10 includes, wherein: the thread create instruction further indicates a number of call arguments; and the call arguments are accessed from registers of the parent thread.
In Example 12, the subject matter of Examples 1-11 includes, wherein: the processing element is a hybrid threading processor.
Example 13 is a non-transitory machine-readable medium that stores instructions that, when executed by a hybrid threading processor, cause the hybrid threading processor to perform operations comprising: receiving a thread create instruction from a parent thread that indicates a number of return parameters to be generated by a child thread created by the thread create instruction; reserving, based on the number of return parameters, space in a memory to store the return parameters; creating the child thread based at least in part on the reserving of the space in the memory; and providing access to the return parameters from the reserved space to the parent thread based at least in part on a thread return instruction from the child thread.
In Example 14, the subject matter of Example 13 includes, wherein: the operations further comprise receiving a join instruction from the parent thread; and the providing of the access to the return parameters from the reserved space to the parent thread is in response to the receipt of the join instruction.
In Example 15, the subject matter of Examples 13-14 includes, wherein the thread create instruction from the parent thread that indicates the number of return parameters uses two bits to indicate the number of return parameters.
In Example 16, the subject matter of Examples 13-15 includes, bits for each return parameter.
In Example 17, the subject matter of Examples 13-16 includes, wherein the providing of the return parameters from the reserved space to the parent thread comprises copying data from the reserved space to a register state of the parent thread.
In Example 18, the subject matter of Examples 13-17 includes, wherein the operations further comprise: in response to the thread return instruction, checking that all operations initiated by the child thread have either completed or been acknowledged.
Example 19 is a method comprising: receiving, by a hybrid threading processor, a thread create instruction from a parent thread that indicates a number of return parameters to be generated by a child thread created by the thread create instruction; reserving, by the hybrid threading processor, based on the number of return parameters, space in a memory to store the return parameters; creating the child thread based at least in part on the reserving of the space in the memory; and providing access to the return parameters from the reserved space to the parent thread based at least in part on a thread return instruction from the child thread.
In Example 20, the subject matter of Example 19 includes, waiting for all threads created by the child thread to complete before sending the thread return instruction from the child thread.
In Example 21, the subject matter of Examples 19-20 includes, wherein the thread create instruction further indicates whether to start the child thread on a local node or a remote node.
In Example 22, the subject matter of Examples 19-21 includes, wherein the creating of the child thread comprises: beginning execution of the child thread from an address read from a register of the parent thread.
In Example 23, the subject matter of Examples 19-22 includes, wherein: the thread create instruction further indicates a number of call arguments; and the call arguments are accessed from registers of the parent thread.
Example 24 is at least one machine-readable medium including instructions that, when executed by processing circuitry, cause the processing circuitry to perform operations to implement any of Examples 1-23.
Example 25 is an apparatus comprising means to implement any of Examples 1-23.
Example 26 is a system to implement any of Examples 1-23.
Example 27 is a method to implement any of Examples 1-23.
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” can include “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first.” “second,” and “third,” and the like are used merely as labels, and are not intended to impose numerical requirements on their objects.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) can be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features can be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter can lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
