Patent Application
20190391851
The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art.
Virtual computing systems are widely used in a variety of applications. Virtual computing systems include one or more host machines running one or more virtual machines concurrently. The one or more virtual machines utilize the hardware resources of the underlying one or more host machines. Each virtual machine may be configured to run an instance of an operating system. Modern virtual computing systems allow several operating systems and several software applications to be safely run at the same time on the virtual machines of a single host machine, thereby increasing resource utilization and performance efficiency. However, present day virtual computing systems still have limitations due to their configuration and the way they operate.
In accordance with some other aspects of the present disclosure, a system is disclosed. The system includes a virtual machine including a guest operating system, at least one guest physical memory, at least one guest physical processor, and at least one guest physical swap storage. The system also includes a physical processing resource including at least one host physical memory, at least one host physical processor, and at least one host physical swap storage. The system also includes a hypervisor mapping the virtual machine to the physical resources. The hypervisor is configured to allocate a first amount of the host physical memory to the guest physical memory. The hypervisor is further configured to receive first page fault information. The hypervisor is also configured to determine, based on the first page fault information, a first page fault rate. The hypervisor is additionally configured to determine that the first page fault rate is greater than a threshold rate, and allocate a second amount, greater than the first amount, of the host physical memory to the guest physical memory.
In accordance with at least some aspects of the present disclosure, a method for managing allocation of a host physical memory of a host computing system to a guest physical memory of a virtual machine running on the host computing system is disclosed. The method includes allocating a first amount of the host physical memory to the guest physical memory of the virtual machine. The method further includes receiving first page fault information. The method also includes determining, based on the first page fault information, a first page fault rate. The method further includes determining that the first page fault rate is greater than a threshold rate, and allocating a second amount, greater than a first amount, of the host physical memory to the guest physical memory.
In accordance with at least some aspects of the present disclosure, a non-transitory computer-readable medium is disclosed. The non-transitory computer-readable medium having instructions stored, the instructions when executed by one or more processors, cause the one or more processors to allocate a first amount of a host physical memory to a guest physical memory, the host physical memory included in a host computing system, the guest physical memory assigned to a virtual machine running on the host computing system. The instructions cause the one or more processors to receive first page fault information. The instructions cause the one or more processors to determine, based on the first page fault information, a first page fault rate. The instructions cause the one or more processors to determine that the first page fault rate is greater than a threshold rate, and allocate a second amount, greater than the first amount, of the host physical memory to the guest physical memory.
The embodiments of the present disclosure are not be limited to a clustered or hyper-converged environment. The aspects of the present disclosure work with a single host in some embodiments.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the following drawings and the detailed description.
The foregoing and other features of the present disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
The present disclosure is generally directed to operating one or more virtual machines in a computing system using a hypervisor. The virtual machines can include an operating system, a guest physical processor, a guest physical memory, and a guest swap disk. The operating system can map virtual memory address space associated with each process to a portion of memory in the guest physical memory. In addition, the hypervisor can map the guest physical memory to a portion of a host physical memory on which the virtual machine is run. A size of the portion of the host physical memory allocated to the guest physical memory is typically predetermined by an administrator or a management module that creates the virtual machine. The administrator or the management module, based in part on a page fault rate and a threshold rate can dynamically change a size of the allocation of the host physical memory to the guest physical memory.
One technical problem encountered in such computing systems is the risk of under- or over-provisioning or under-allocating the host physical memory to the guest physical memory of the virtual machines. In some instances, the administrator or the management module may under-provision memory allocation to a virtual machine. That is, the amount of host physical memory allocated to the guest physical memory of the virtual machine is considerably less than that needed by virtual machine. This may result in repeated page faults, which can have adverse performance impact on the operation of the under-provisioned virtual machine. On the other hand, in some other instances, the administrator or the management module may over-provision or over-allocate the host physical memory to the guest physical memory of the virtual machine. That is, the amount of host physical memory allocated to the guest physical memory of the virtual machine is considerably greater than that needed by the virtual machine. While this may not have direct adverse impact the performance of the virtual machine, the over allocation may result in a less than ideal density of virtual machines being supported by the physical resources of the host. Another technical problem encountered in such computing systems is inability on the part of the administrator or the management module, to dynamically determine under- or over-provisioning and adjust the guest physical memory allocation to individual virtual machines.
The discussion below provides at least one solution to the technical problems mentioned above. For example, the hypervisor is configured to monitor a number of major page faults generated due to requested memory pages being absent in the host physical memory and instead being present in storage device. The hypervisor is configured to generate a page fault rate based on the number of page faults over a predetermined time period. The hypervisor compares the page fault rate with a threshold rate. If the measured page fault rate is greater than the threshold rate, the hypervisor can determine that the guest physical memory has been under-provisioned. The hypervisor can also increase a size of the portion of the host physical memory allocated to the guest physical memory. By increasing the allocation, the risk of page faults can be decreased, thereby potentially improving the performance of the virtual machine. The hypervisor can also be configured to determine whether the guest physical memory has been over-provisioned. The hypervisor can determine whether the page fault rate is less than or equal to the threshold rate. The page fault rate being greater than the threshold rate can indicate that the guest physical memory has been over-provisioned. The hypervisor can be configured to decrease the size of the portion of the host physical memory that is allocated to the guest physical memory of the virtual machine.
Referring now to
The virtual computing system 100 may also include a storage pool 140. The storage pool 140 may include network-attached storage 145 and direct-attached storage 150. The network-attached storage 145 may be accessible via the network 135 and, in some embodiments, may include cloud storage 155, as well as local storage area network 160. In contrast to the network-attached storage 145, which is accessible via the network 135, the direct-attached storage 150 may include storage components that are provided within each of the first node 105, the second node 110, and the third node 115, such that each of the first, second, and third nodes may access its respective direct-attached storage without having to access the network 135.
It is to be understood that only certain components of the virtual computing system 100 are shown in
Although three of the plurality of nodes (e.g., the first node 105, the second node 110, and the third node 115) are shown in the virtual computing system 100, in other embodiments, greater or fewer than three nodes may be used. Likewise, although only two of the user VMs 120 are shown on each of the first node 105, the second node 110, and the third node 115, in other embodiments, the number of the user VMs on the first, second, and third nodes may vary to include either a single user VM or more than two user VMs. Further, the first node 105, the second node 110, and the third node 115 need not always have the same number of the user VMs 120. Additionally, more than a single instance of the hypervisor 125 and/or the controller/service VM 130 may be provided on the first node 105, the second node 110, and/or the third node 115.
Further, in some embodiments, each of the first node 105, the second node 110, and the third node 115 may be a hardware device, such as a server. For example, in some embodiments, one or more of the first node 105, the second node 110, and the third node 115 may be an NX-1000 server, NX-3000 server, NX-6000 server, NX-8000 server, etc. provided by Nutanix, Inc. or server computers from Dell, Inc., Lenovo Group Ltd. or Lenovo PC International, Cisco Systems, Inc., etc. In other embodiments, one or more of the first node 105, the second node 110, or the third node 115 may be another type of hardware device, such as a personal computer, an input/output or peripheral unit such as a printer, or any type of device that is suitable for use as a node within the virtual computing system 100.
Each of the first node 105, the second node 110, and the third node 115 may also be configured to communicate and share resources with each other via the network 135. For example, in some embodiments, the first node 105, the second node 110, and the third node 115 may communicate and share resources with each other via the controller/service VM 130 and/or the hypervisor 125. One or more of the first node 105, the second node 110, and the third node 115 may also be organized in a variety of network topologies, and may be termed as a “host” or “host machine.”
Also, although not shown, one or more of the first node 105, the second node 110, and the third node 115 may include one or more processing units configured to execute instructions. The instructions may be carried out by a special purpose computer, logic circuits, or hardware circuits of the first node 105, the second node 110, and the third node 115. The processing units may be implemented in hardware, firmware, software, or any combination thereof. The term “execution” is, for example, the process of running an application or the carrying out of the operation called for by an instruction. The instructions may be written using one or more programming language, scripting language, assembly language, etc. The processing units, thus, execute an instruction, meaning that they perform the operations called for by that instruction.
The processing units may be operably coupled to the storage pool 140, as well as with other elements of the respective first node 105, the second node 110, and the third node 115 to receive, send, and process information, and to control the operations of the underlying first, second, or third node. The processing units may retrieve a set of instructions from the storage pool 140, such as, from a permanent memory device like a read only memory (ROM) device and copy the instructions in an executable form to a temporary memory device that is generally some form of random access memory (RAM). The ROM and RAM may both be part of the storage pool 140, or in some embodiments, may be separately provisioned from the storage pool. Further, the processing units may include a single stand-alone processing unit, or a plurality of processing units that use the same or different processing technology.
With respect to the storage pool 140 and particularly with respect to the direct-attached storage 150, it may include a variety of types of memory devices. For example, in some embodiments, the direct-attached storage 150 may include, but is not limited to, any type of RAM, ROM, flash memory, magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., compact disk (CD), digital versatile disk (DVD), etc.), smart cards, solid state devices, etc. Likewise, the network-attached storage 145 may include any of a variety of network accessible storage (e.g., the cloud storage 155, the local storage area network 160, etc.) that is suitable for use within the virtual computing system 100 and accessible via the network 135. The storage pool 140 including the network-attached storage 145 and the direct-attached storage 150 may together form a distributed storage system configured to be accessed by each of the first node 105, the second node 110, and the third node 115 via the network 135 and the controller/service VM 130, and/or the hypervisor 125. In some embodiments, the various storage components in the storage pool 140 may be configured as virtual disks for access by the user VMs 120.
Each of the user VMs 120 is a software-based implementation of a computing machine in the virtual computing system 100. The user VMs 120 emulate the functionality of a physical computer. Specifically, the hardware resources, such as processing unit, memory, storage, etc., of the underlying computer (e.g., the first node 105, the second node 110, and the third node 115) are virtualized or transformed by the hypervisor 125 into the underlying support for each of the plurality of user VMs 120 that may run its own operating system and applications on the underlying physical resources just like a real computer. By encapsulating an entire machine, including CPU, memory, operating system, storage devices, and network devices, the user VMs 120 are compatible with most standard operating systems (e.g. Windows, Linux, etc.), applications, and device drivers. Thus, the hypervisor 125 is a virtual machine monitor that allows a single physical server computer (e.g., the first node 105, the second node 110, and third node 115) to run multiple instances of the user VMs 120, with each user VM sharing the resources of that one physical server computer, potentially across multiple environments. By running the plurality of user VMs 120 on each of the first node 105, the second node 110, and the third node 115, multiple workloads and multiple operating systems may be run on a single piece of underlying hardware computer (e.g., the first node, the second node, and the third node) to increase resource utilization and manage workflow.
The user VMs 120 are controlled and managed by the controller/service VM 130. The controller/service VM 130 of each of the first node 105, the second node 110, and the third node 115 is configured to communicate with each other via the network 135 to form a distributed system 165. The hypervisor 125 of each of the first node 105, the second node 110, and the third node 115 may be configured to run virtualization software, such as, ESXi from VMWare, AHV from Nutanix, Inc., XenServer from Citrix Systems, Inc., etc., for running the user VMs 120 and for managing the interactions between the user VMs and the underlying hardware of the first node 105, the second node 110, and the third node 115. The controller/service VM 130 and the hypervisor 125 may be configured as suitable for use within the virtual computing system 100.
The network 135 may include any of a variety of wired or wireless network channels that may be suitable for use within the virtual computing system 100. For example, in some embodiments, the network 135 may include wired connections, such as an Ethernet connection, one or more twisted pair wires, coaxial cables, fiber optic cables, etc. In other embodiments, the network 135 may include wireless connections, such as microwaves, infrared waves, radio waves, spread spectrum technologies, satellites, etc. The network 135 may also be configured to communicate with another device using cellular networks, local area networks, wide area networks, the Internet, etc. In some embodiments, the network 135 may include a combination of wired and wireless communications.
Referring still to
The first user VM 202 also can include one or more guest physical processers, guest physical memories, and guest swap disks. For example, the first user VM 202 can include a first guest physical processor (GPP1) 216, a first guest physical memory (GPM1) 218, and a first guest swap disk (GSwap1) 220. Similarly, the second user VM 204 can include a second guest physical processor (GPP2) 222, a second guest physical memory 224, and a second guest swap disk 226. The number of guest physical processors, guest physical memories, and guest swap disks shown in
The hypervisor 206 can implement processor, memory, and storage virtualization by abstracting the hardware resources 208 including processors, memory, and I/O devices, and present the abstraction to the first and the second user VMs 202 and 204 as the guest physical processors, guest physical memories and guest swap disks. For example, the hypervisor 206 can implement processor virtualization by scheduling time slots on one or more physical processors of the hardware resources 208 such that from the guest OS's perspective, the time slots are scheduled on the guest physical processors. The hypervisor 206 can implement memory virtualization by maintaining a translation table that translates memory addresses assigned by the guest OSs to physical memory addresses in the physical memories of the hardware resources 208.
The hardware resources 208 can include several processors and memories. While not shown in
Each guest OS in the user VMs can provide a virtual memory space to the one or more processes running on the guest OS. For example, the first guest OS 210 can provide a virtual memory space in a first virtual memory to each of the four processes P1-P4212 running on the first guest OS 210. Similarly, the second guest OS 214 can provide a virtual memory space in a second virtual memory to each of the four processes P5-P8256 running on the second guest OS 214. The virtual memory space provided to the processors can be divided into blocks of a certain size (such as, for example, 4 kB) and can be referred to as pages. Each guest OS maps the virtual memory space provided to each processor to the respective guest physical memory. For example, the first guest OS 210 can map the virtual memory space provided to each process in the first set of processes 212 to memory locations in the GPM1218. Similarly, the second guest OS 214 can map the virtual memory space provided to each process in the second set of processes 256 to memory locations in the GPM2224. The information mapping the virtual memory space seen by the processes to the guest physical memory can be stored in page table. The guest OS can create a page table for each process, and map the virtual memory addresses within the virtual memory space provided to that process to memory locations in the guest physical memory. For example, the first guest OS 210 can generate a page table for each of the four processes in the first set of processes 212. Whenever a process is being executed, the guest OS can load the page table corresponding to that process to determine addresses mappings to the guest physical memory.
The hypervisor 206 also maintains a memory map. Specifically, the hypervisor 206 stores memory mapping between the guest physical memories (GPM1218 and GPM2224) and the host physical memory 230 in the hardware resources 208 of the host. The hypervisor 206 can store this mapping information in a physical mapping table, which maps memory locations in the guest physical memories to the host physical memories. Thus, the combined mapping information included in the page tables and the physical mapping table can provide mapping between the virtual memory space seen by a process and the physical memory location in the host physical memory.
The hypervisor 206 may also maintain a mapping between the guest physical storage and the host physical storage. For example, the hypervisor 206 can store mapping information between storage addresses in the GSwap1220 and the corresponding addresses in the HSwap 232. Similarly, the hypervisor can also store mapping information between the addresses in the GSwap2226 and the corresponding addresses in the HSwap 232.
The hypervisor 206 can allocate a certain amount of host physical memory 230 to each of the guest physical memories. For example, the hypervisor 206 can allocate a portion of the host physical memory 230 to the guest physical memory GPM1218 of the first user VM 202, and another portion of the host physical memory 230 to the guest physical memory GPM2224 of the second virtual machine 204. In this manner, the hypervisor 206 can distribute the available host physical memory 230 to the one or more virtual machines supported by the hypervisor 206.
The sizes of the portions of the host physical memory 230 allocated to the first guest physical memory 218 and the second guest physical memory 224 can have an impact on the performance of the respective virtual machines and the node 200. For example, if the allocation is relatively smaller than the memory address space frequently accessed by a guest physical memory, then the hypervisor 206 or the memory management unit of the host may have to swap-out pages in the host physical memory 230 into the host swap storage 232. Thus, the next time a process running on the virtual machine accesses an address space that maps to the swapped out page in the host physical memory, the host physical processor 228 may generate a major page fault. Upon generation of the major page fault, the hypervisor 206, or the memory management unit of the node 200, can swap-in the requested page from the host swap storage 232 back into the host physical memory 230. If the host physical memory 230 is full, another portion of the host physical memory 230 including other pages may have to be swapped-out to the host swap storage 232 to make space for the swapped-in pages. The swapping-in and swapping-out of the pages between the host physical memory 230 and the host swap storage 232 can adversely impact the performance of the virtual machine. One approach to reducing the number of page faults is to increase the size of the portion of the host physical memory 230 allocated to the virtual machine. However, increasing the allocation may result in over-provisioning if the added allocation of host physical memory space goes under-utilized. As a result, the density of the virtual machines supported by the host physical memory 230 may be lower than what can be actually accommodated.
The process further includes receiving first page fault information (404). The hypervisor 206 can receive first page fault information on page faults related to the host physical memory 230. For example, the first guest OS 210 of the first user VM 202 may request to read or write data in a particular address space. If the memory page associated with the address space is not located in the host physical memory 230, but is instead located in the host swap storage 232, or other physical storage, a page fault can occur. The host physical processor 228 can generate an exception in response to determining that the requested page is not located in the host physical memory 230 and that it is instead located in the host swap storage 232 or other storage. This exception can constitute a page fault. The exceptions generated by the host physical processor 228 can be monitored by the hypervisor 206. In some examples, the hypervisor 206 can repeatedly monitor the occurrence of page faults over time to determine a rate of page faults.
The page fault information received by the hypervisor 206 can include the page fault numbers received at one or more instances. For example, the page fault information received by the hypervisor can include the page fault numbers PF1 and PF2 received at time instances T1 and T2. The hypervisor 206 can be configured to poll and receive page fault information related to more than one virtual machine. For example, the hypervisor 206 can receive page fault information associated with the first user VM 202 and page fault information associated with the second user VM 204. The hypervisor 206 can store the received page fault information associated with each virtual machine in memory. For example, the hypervisor 206 can store the page fault information for the respective virtual machines over a period of time, such as, for example, 1 minute to about 2 minutes, or longer.
The process 400 also includes determining, based on the page fault information, a first rate of page faults (406). The hypervisor 206 can determine a first rate of page faults associated with a virtual machine based on the page fault information, such as the number of page faults at one or more time instances. In some examples, the hypervisor 206 can be configured to determine the rate of page faults per unit of time, where the unit of time can be in milliseconds, seconds, minutes, or any other unit of time. Based on the desired unit of time over which the rate is to be determined, and the instances over which the page fault information is received, the hypervisor 206 can determine a first page fault rate. As an example, referring to
The hypervisor 206 can maintain page fault rate values for each of the virtual machines supported by the hypervisor 206. For example,
The process 400 additionally includes determining that the first rate of page faults is greater than a threshold rate (408). The hypervisor 206 can store in memory a threshold rate that can be representative of a value which if exceeded can be indicative of degraded performance of the virtual machine. In some examples, the threshold rate can be experimentally determined to balance performance, memory usage, and convergence rate. The threshold rate may be scaled linearly with the number of guest processors. R=k*P+c (where P is the number of guest processors, and k and c are constants determined experimentally). In some examples, the threshold rate can be a constant. In some examples, the threshold rate can be varied based on various parameters of the virtual machine. For example, the threshold rate can be a function of the number of guest physical processors (e.g., GPP1216) in the virtual machine. However, the process 400 is not specific to a clustered or hyper-converged environment and would work with a single host. In some examples, the threshold rate can increase linearly with the number of guest physical processors in the virtual machine.
The process 400 also includes allocating a second amount, greater than the first amount, of the host physical memory to the guest physical memory (410). The hypervisor 206 can determine that the page fault rate associated with a virtual machine is greater than a threshold value. This can indicate that the performance of the associated virtual machine is being adversely impacted by the size of the portion of the host physical memory allocated to the virtual machine. One approach to reducing the number of page faults is to allocate a larger portion of the host physical memory to the virtual machine. For example, referring to
The hypervisor 206 can continue to monitor the page fault rate associated with the first virtual machine “VM1,” over time, and continue to incrementally increase the allocation to the virtual machine until the page fault rate is less than or equal to the threshold rate. In some examples, the hypervisor 206 can monitor the page fault rate at a higher frequency during the increase in the allocation until the page fault rate is equal to or greater than the threshold rate. In some examples, the hypervisor 206 can determine the size of increase in the allocation based on the severity of the page fault rate. For example, the hypervisor 206 can determine the increase in allocation as a function of the difference between the determined page fault rate and the threshold value. In some examples, the hypervisor 206 can determine the increase in the allocation to be proportional to the difference between the determined page fault rate and the threshold value. Thus, greater the difference between the page fault value and the threshold rate, greater is increase in allocation of the host physical memory to the virtual machine. Thus, at a given time, the hypervisor 206 can increase the allocation by a certain amount based on the difference between the page fault rate and the threshold value. Due to the increase in allocation, the page fault rate may decrease in the next instance that the page fault rate is determined. As the difference between the page fault rate and the threshold rate is decreased, the hypervisor 206, while still increasing the allocation to the virtual machine, may reduce the amount by which the allocation is increased. In some examples, the hypervisor 206 can increase the allocation by a constant amount each time the hypervisor 206 determines that the page fault rate is greater than the threshold value.
In some instances, the hypervisor 206 can decrease the allocation of host physical memory to the virtual machine responsive to determining that the page fault rate is less than or equal to the threshold value. For example, determining that the page fault value is less than or equal to the threshold value may indicate that the guest physical memory is being over-provisioned. The over-provisioning of the guest physical memory can reduce the efficiency of the node 200. For example, due to the over-provisioning, the node 200 may be supporting a fewer number of virtual machines that it actually can. To improve the virtual machine density on the node 200, the hypervisor 206 can decrease the allocation or de-allocate the amount of host physical memory to the guest physical memory of the virtual machine. Thus, for example, assuming the threshold rate is 10, and the current page fault rate is 8, which is less than the threshold rate. As a result, the hypervisor 206 can decrease the allocation from, say, e.g., 4 GB to 3 GB. The de-allocation of the amount of host physical memory to the virtual machine may continue if the page fault rate continues to remain below or equal to the threshold rate. The hypervisor 206 can use the de-allocated amount of host physical memory for allocation to an additional virtual machine, or to increase the allocation to an existing virtual machine that is perhaps experiencing page fault rates that are greater than the threshold value.
In some examples, the hypervisor 206 may decrease allocation relatively slowly than the rate at which it increases allocation. For example, the hypervisor 206 can increase allocation every time the hypervisor 206 determines that the page fault rate is greater than the threshold value. In some scenarios, this can mean that the hypervisor 206 increases allocation each time the page fault number is polled and the determined page fault rate is still greater than the threshold rate. On the other hand, the hypervisor 206 may decrease allocation of the amount of host physical memory at a relatively slower rate. For example, the hypervisor 206 can set a delay time period between any two successive decreases the allocation for a virtual machine, where the delay time period is greater than the polling time period.
While the examples above have been discussed in relation to one virtual machine, it is understood that the hypervisor 206 can simultaneously dynamically control the allocation and de-allocation of host physical memory to more than one virtual machine. For example, referring to
It is to be understood that in some embodiments, any of the operations described herein may be implemented at least in part as computer-readable instructions stored on a computer-readable memory. Upon execution of the computer-readable instructions by a processor, the computer-readable instructions may cause a node to perform the operations.
The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” Further, unless otherwise noted, the use of the words “approximate,” “about,” “around,” “substantially,” etc., mean plus or minus ten percent.
The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
