Patent Application
20070198750
1. Field of the Invention
The present invention relates generally to an improved data processing system, in particular, to a computer implemented method, a data processing system, and a computer program product for optimizing performance in a data processing system. Still more particularly, the present invention provides a computer implemented method, a data processing system, and a computer program product for input/output workload fingerprinting for input/output schedulers.
2. Description of the Related Art
Input/output schedulers (I/O schedulers) can increase the performance of input/output (I/O) throughput of a system dramatically by tuning the I/O scheduler parameters based on the current workload of the system. The input/output requests scheduled by an I/O scheduler for a system is the I/O workload of the system. A tunable parameter for the I/O scheduler is a parameter that affects the operation of an I/O scheduler. This type of parameter may be changed dynamically while the I/O scheduler is operating. The I/O scheduler parameters may include tunable parameters, such as a default read expire time-out period, a default write batch expire time-out period, and a write queue depth. However, the workload is very difficult for the I/O scheduler to classify because the I/O scheduler only examines a small perspective of what is occurring in the system. If an I/O scheduler could classify the actual current workload, the I/O scheduler could operate much more efficiently by tuning the I/O scheduler parameters based on the current workload of the system.
A common attempt at classifying workloads is made by attempting to recognize a sequential read operation through read-ahead classification. The idea of read-ahead classification is to increase the disk read ahead size by observing a pattern in which a single application accesses a single file on the disk.
Another common attempt at classifying workloads is made by an anticipatory I/O scheduler. This I/O scheduler breaks down all I/O requests for all applications into either a read request or a write request. If the current request is a read request, then the typical anticipatory I/O scheduler will run an adaptive heuristic algorithm (an approximation algorithm) on the probability that another read request will occur that accesses a sector that is a small seek distance away from the sector to be accessed by the current read request, even if the sector to be accessed is for a different file.
The aspects of the present invention provide a computer implemented method, a data processing system, and a computer program product for input/output workload fingerprinting for input/output schedulers. Requests are identified in a workload for an input/output scheduler. Each request is classified to form a set of classifications. Whether an action is needed is determined based on the set of classifications. If the action is needed, the action is initiated.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as an illustrative mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
With reference now to the figures,
In the depicted example, server 104 and server 106 connect to network 102 along with storage unit 108. In addition, clients 110, 112, and 114 connect to network 102. These clients 110, 112, and 114 may be, for example, personal computers or network computers. In the depicted example, server 104 provides data, such as boot files, operating system images, and applications to clients 110, 112, and 114. Clients 110, 112, and 114 are clients to server 104 in this example. Network data processing system 100 may include additional servers, clients, and other devices not shown.
In the depicted example, network data processing system 100 is the Internet with network 102 representing a worldwide collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, governmental, educational, and other computer systems that route data and messages. Of course, network data processing system 100 also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).
With reference now to
In the depicted example, data processing system 200 employs hub architecture including north bridge and memory controller hub (NB/MCH) 202 and south bridge and input/output (I/O) controller hub (SB/ICH) 204. Processing unit 206, main memory 208, and graphics processor 210 are connected to NB/MCH 202. Graphics processor 210 may be connected to NB/MCH 202 through an accelerated graphics port (AGP).
In the depicted example, local area network (LAN) adapter 212 connects to SB/ICH 204. Audio adapter 216, keyboard and mouse adapter 220, modem 222, read only memory (ROM) 224, hard disk drive (HDD) 226, CD-ROM drive 230, universal serial bus (USB) ports and other communication ports 232, and PCI/PCIe devices 234 connect to SB/ICH 204 through bus 238 and bus 240. PCI/PCIe devices may include, for example, Ethernet adapters, add-in cards and PC cards for notebook computers. PCI uses a card bus controller, while PCIe does not. ROM 224 may be, for example, a flash binary input/output system (BIOS).
HDD 226 and CD-ROM drive 230 connect to SB/ICH 204 through bus 240. HDD 226 and CD-ROM drive 230 may use, for example, an integrated drive electronics (IDE) or serial advanced technology attachment (SATA) interface. Super I/O (SIO) device 236 maybe connected to SB/ICH 204.
An operating system runs on processing unit 206 and coordinates and provides control of various components within data processing system 200 in
As a server, data processing system 200 may be, for example, an IBM® eServer™ pSeries® computer system, running the Advanced Interactive Executive (AIX®) operating system or the LINUX® operating system (eServer, pSeries and AIX are trademarks of International Business Machines Corporation in the United States, other countries, or both while LINUX is a trademark of Linus Torvalds in the United States, other countries, or both). Data processing system 200 may be a symmetric multiprocessor (SMP) system including a plurality of processors in processing unit 206. Alternatively, a single processor system may be employed.
Instructions for the operating system, the object-oriented programming system, and applications or programs are located on storage devices, such as HDD 226, and may be loaded into main memory 208 for execution by processing unit 206. The processes for embodiments of the present invention are performed by processing unit 206 using computer usable program code, which may be located in a memory such as, for example, main memory 208, ROM 224, or in one or more peripheral devices 226 and 230.
Those of ordinary skill in the art will appreciate that the hardware in
In some illustrative examples, data processing system 200 may be a personal digital assistant (PDA), which is configured with flash memory to provide non-volatile memory for storing operating system files and/or user-generated data.
A bus system may be comprised of one or more busses, such as bus 238 or bus 240 as shown in
Embodiments of the present invention may be implemented using components of the network for the data processing system in
Embodiments of the present invention monitor and classify workloads for an input/output scheduler in order to tune the input/output scheduler to work more efficiently. After monitoring input/output requests for a pre-defined amount of time, a classification algorithm identifies a workload characteristic for the input/output requests and classifies the workload based upon the workload characteristic. The classification algorithm executes the identifying and classifying steps for different workload characteristics. Then the classification algorithm adjusts tunable parameters for the input/output scheduler based on the classifications of the workload.
Embodiments of the present invention provide the ability to determine a “fingerprint” for a system's I/O workload. This fingerprinting is achieved by a classification algorithm breaking down the workload monitored during a pre-defined amount of time into small measurable characteristics, classifying the small measurable characteristics, and then assembling the classifications of the small characteristics into a fingerprint, such as fingerprint 320. A workload characteristic is one of many small measurable characteristics of a workload that may be measured based upon monitoring input/output requests. Examples of workload characteristics include the ratio of read requests to write requests, the seek distance between requests, and the average size of the requests. With all components residing in operating system 330, classification algorithm 300 assembles fingerprint 320 from classifications of workload characteristics to enable I/O schedulers, such as I/O scheduler 310, to achieve a number of goals. Through the use of fingerprint 320, classification algorithm 300 may swap the current I/O scheduler, such as I/O scheduler 310, for another I/O scheduler, such as I/O scheduler 340 or I/O scheduler 350. Alternatively, classification algorithm 300 may tune the I/O scheduler parameters to pre-defined settings for the tunable parameters based upon the workload. As discussed above, examples of tunable parameters may include a default read expire time-out period, a default write batch expire time-out period, and a write queue depth. The maximum default read expire time-out period and the minimum read expire time-out period are examples of parameters that are not tunable.
Finger print 320 generated for a particular workload of I/O requests may consist of a number of classifications. An illustrative example of a simple fingerprint, such as fingerprint 320, may include many classifications in addition to three general classifications. These three general classifications based on workload characteristics are I/O access type 322, which may be read or write, I/O access pattern 324, which may be sequential or random, and I/O access size 326, which may be large or small.
By classifying the workload based upon multiple classifications of workload characteristics, the classification algorithm generates a fingerprint to inform the current I/O scheduler how to operate more efficiently. I/O workload fingerprinting differs from the read-ahead classification because I/O workload fingerprinting examines all of the I/O occurring on a device, such as hard disk 314. A read-ahead classification only examines one particular file on a device, and does not take into account the rest of the I/O on the device. The broader perspective offered by the classification algorithm for I/O workload fingerprinting is a more accurate reflection of the device's workload.
I/O workload fingerprinting differs from the typical anticipatory I/O scheduler in several aspects. For example, unlike the classification algorithm for I/O workload fingerprinting, the typical anticipatory I/O scheduler does not examine I/O access size for I/O requests. The typical anticipatory I/O scheduler does not attempt to classify a request once the typical anticipatory I/O scheduler has determined that the request is a write request. The typical anticipatory I/O scheduler only attempts to classify read requests based upon what would be comparable to a sequential read request by examining the current disk head position. If a set of sequential read requests occurs, and these read requests are for sectors far from the current disk head position, the typical anticipatory I/O scheduler's heuristic does not determine that the access pattern is sequential. The classification algorithm for I/O workload fingerprinting examines all the sector distances for requests in order to determine an access pattern.
The classification algorithm for I/O workload fingerprinting uses the block layer of an operating system to monitor input/output requests, examine different characteristics of the input/output requests for an I/O workload and classifies these characteristics to create a fingerprint of the current workload type. The block layer of an operating system is the layer of the kernel that services I/O requests in blocks, such as a block of 512 bytes or a block of 4096 bytes, rather than servicing I/O requests based on characters. All operating systems that access hard disks have a block layer to service I/O requests. I/O schedulers and the classification algorithm are part of the block layer of an operating system. I/O workload fingerprinting may be implemented in a number of ways.
In response to the classification algorithm for I/O workload fingerprinting monitoring the I/O requests, the classification algorithm classifies the current workload based on the classifications of the workload characteristics determined. The classification algorithm identifies a workload characteristic for the I/O requests (step 404). Based upon the determination of a workload characteristic, the classification algorithm classifies the workload (step 406). Implementation of the identification step and the classification step are detailed further below in
When the classification algorithm decides to swap the current I/O scheduler for another I/O scheduler, the classification algorithm stops the current I/O scheduler from accessing incoming I/O requests from the incoming I/O requests buffer. Next, the classification algorithm waits until the current I/O scheduler empties its queues of I/O requests. Then, the classification algorithm switches the operating system's function pointers from the current I/O scheduler to the next I/O scheduler. Finally, the classification algorithm initiates the new I/O scheduler to retrieve incoming I/O requests from the incoming I/O requests buffer. Details and examples of when the classification algorithm swaps I/O schedulers are listed further below in the discussion that follows immediately after the references to
In another example of a workload characteristic, the seek distance between requests may be used to classify the access pattern because a sequential access pattern occurs when requests are for sectors normally close in proximity to each other while a random access pattern occurs when requests are for sectors spread across the disk. The classification algorithm identifies if the average seek distance between requested sectors is below a pre-determined threshold (step 508). If the average seek distance is below a pre-determined threshold, the classification algorithm classifies the workload as a sequential workload (step 510). If the average seek distance is equal to or above the pre-determined threshold, then the classification algorithm classifies the workload as a random workload (step 512).
In yet another example of a workload characteristic, the average size of the requests during the time slice may be used to classify the workload as large or small. The classification algorithm identifies if the average size of the requests is equal to or above a pre-determined threshold (step 514). If the request size is equal to or above a pre-determined threshold, the classification algorithm classifies the workload as a large workload (step 516). If the request size is below the pre-determined threshold, then the classification algorithm classifies the workload as a small workload (step 518). In one embodiment of the present invention, the workload characteristics that are classified by the classification algorithm are hard-coded into the process. In another embodiment of the present invention, the workload characteristics that are classified by the classification algorithm are listed in a process file that supplies the classification algorithm with a checklist. The user may modify the process file that determines which workload characteristics the classification algorithm classifies.
While many combinations exist for I/O workload fingerprints, fingerprints assembled from classifications based on the examples illustrated above may include sequential-large-reads and random-small-reads. Once the classification algorithm assembles an I/O workload fingerprint, the classification algorithm may adjust tunable parameters, and/or may swap the current I/O scheduler for another I/O scheduler.
The classification algorithm has the option of executing the process illustrated in
For example, if the classification algorithm classifies a workload as a random-small-write workload, after any adjustments to tunable parameters, the classification algorithm may swap the current anticipatory I/O scheduler for a deadline I/O scheduler, a more efficient I/O scheduler for a random-small-write workload. If the classification algorithm classifies a workload as a large-sequential-read workload, after any adjustments to tunable parameters the classification algorithm may swap the current complete fair queuing I/O scheduler for an anticipatory I/O scheduler, a more efficient I/O scheduler for a large-sequential-read workload.
After the classification algorithm adjusts tunable parameters, and/or swaps the current I/O scheduler for another I/O scheduler, the classification algorithm monitors more I/O requests over a pre-determined amount of time. Then I/O workload fingerprinting process repeats itself.
Overall, embodiments of the present invention solve a problem that is not addressed using currently available approaches. The process as shown in
The invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment containing both hardware and software elements. In an illustrative embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc.
Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device), or a propagation medium. Examples of a computer-readable medium include a semiconductor, a solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W), and digital video disc (DVD).
A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution.
Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers.
Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modems, and Ethernet cards are just a few of the currently available types of network adapters.
The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
