HP Virtual Server Environment: Tips for Application Developers

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HP Virtual Server Environment: tips for Application

Developers

Optimizing Applications for Virtualized Environments on HP Integrity and HP9000

servers running HP-UX

HP Virtual Server Environment and ISV Applications ................................................................................ 2

Introduction......................................................................................................................................... 2

Key Terms ........................................................................................................................................... 3

How Resource Migrations Work............................................................................................................ 5

Whole core Granularity Partitions ...................................................................................................... 5

nPars .......................................................................................................................................... 5

vPars........................................................................................................................................... 5

Resource Partitions based on Processor Sets .................................................................................... 5

Sub-Core Partitions ........................................................................................................................... 6

HP Integrity Virtual Machines......................................................................................................... 6

Resource Partitions based on Fair Share Scheduler........................................................................... 6

Memory Migration ........................................................................................................................... 7

Effects of VSE on Applications ............................................................................................................... 7

Performance in a Virtual Server Environment ....................................................................................... 7

Compatibility on HP Integrity Virtual Machines .................................................................................... 7

Topology Aware Applications ........................................................................................................... 8

Optimizing Applications for VSE ........................................................................................................... 8

How many cores, right now?............................................................................................................. 9

How many cores, maximum?............................................................................................................. 9

Tell me when it changes.................................................................................................................. 10

Running Applications Inside a Virtual Machine...................................................................................... 11

Deploying Applications with Workload Managers................................................................................. 12

Conclusion........................................................................................................................................ 12

References ........................................................................................................................................ 12

Appendix A - Using the mpctl() Call .................................................................................................... 13

Appendix B – Assessing application performance in a VSE..................................................................... 14

Summary of content (15 pages)

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HP Virtual Server Environment: tips for Application Developers Optimizing Applications for Virtualized Environments on HP Integrity and HP9000 servers running HP-UX HP Virtual Server Environment and ISV Applications ................................................................................ 2 Introduction......................................................................................................................................... 2 Key Terms ..................................................
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HP Virtual Server Environment and ISV Applications The HP Virtual Server Environment (VSE), HP’s integrated virtualization solution for HP Integrity and HP 9000 servers, provides the flexible capacity that can help IT departments increase their return on IT investments and be more agile at the same time. HP VSE allows real time optimization of server utilization by creating virtual servers that can automatically grow and shrink based on business priorities and service-level objectives.
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Four component areas make up the HP Virtual Server Environment: (1) partitioning, (2) high availability solutions, (3) utility pricing and (4) management and control software. A VSE solution is architected by combining one or more components from two or more of these areas to address a specific set of requirements (such as flexibility, availability, granularity, and isolation).
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 The term SPU is used in some OS interfaces. The term is used for compatibility reasons, but refers to a schedulable hardware entity. If LCPUs are enabled, an SPU is an LCPU. If LCPUs are not enabled, an SPU is a core.  Integrity Virtual Machines use the term “Virtual CPU”. It would be more correctly described as a virtual SPU.
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How Resource Migrations Work Let’s take a look at how core migrations work in the different types of partitions. For this discussion, we separate out the whole core granularity partitions from the sub-core granularity partitions. Whole core Granularity Partitions This section covers partitions that allocate whole cores. In these partition types the number of cores that are visible to an application can vary.
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creation of a pset results in a pset with no processors. Therefore, it is necessary to add processors to the pset before it can run processes. Applications that are designed to be aware of the number of cores should take into consideration the dynamic nature of the VSE environment. For example, an application that allocates one thread per core, should consider the possibility that cores could be removed or more cores could be allocated.
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Memory Migration Memory migration is a new feature of 11i v3. At first release memory can be removed from or added to (hence migrated between) vPars. The first release of Integrity VM after 11i v3 will also include support for adding or removing memory from an Integrity VM guest OS. On a vPar, memory can be allocated as Interleaved Memory (ILM) or Cell Local Memory (CLM), and specific memory ranges can be added or deleted.
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from the host. All mass storage is visible to guests as SCSI disks, regardless of the physical connection. Applications that depend on devices not yet virtualized by Integrity VM will not run in a virtual machine. The devices not yet virtualized include: tape drives, Fibre Channel HBAs, storage array controllers and USB. (Few applications depend on specific device dependencies.) Note that these limitations apply only to Integrity VMs.
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traditional HP-UX scheduling. Additional cores allocated to these applications will be assigned a portion of the work, increasing the overall throughput of the application. How many cores, right now? For applications that need to know the core count, the first thing to determine is the number of cores available “right now”. An application can determine the number of available cores by using the mpctl() call (see mpctl(2) for additional details).
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max_lcpus = buf.psd_max_proc_cnt; printf("Max cores: %d; Max LCPUs: %d\n", max_cores, max_lcpus); } These maximum counts take into account all possible sources of additional CPU resources, including the sum of all psets, all available iCAP processors, and all cores that can be migrated from another vPar. Note that on a Montecito system, the max number of LCPUs will always be twice the max number of cores, whether HyperThreads are enabled or not.
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The most flexible solution is to dynamically react to changes in system resource levels. Consider this approach:  Application starts up, low system load, minimum CPU resources allocated to this partition.  Application queries OS regarding maximum number of cores, allocates two threads per core to handle workload.  Application queries OS regarding current number of cores, assigns work to two threads per active core, optimizing context switching, hence performance.
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Host via one of the methods described below, e.g., iCAP activations or deactivations. Increasing the total number of cores will automatically benefit the virtual machines running on the physical system because the virtual CPUs will appear to run "faster" because they have more physical core cycles allocated to them over time. Optimizing storage and I/O in a virtual machine requires special consideration.
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(http://h21007.www2.hp.com/dev/ ) 3. HP Serviceguard Developer's Toolbox (http://h21007.www2.hp.com/dspp/tech/tech_TechSoftwareDetailPage_IDX/1,1703, 7445,00.html?jumpid=reg_R1002_USEN) 4. VSE RA Best Practices white paper (http://h21007.www2.hp.com/dspp/files/unprotected/hpux/VSE-Ref-Arch-BestPractices.pdf ) 5. Partitioning Continuum (http://h71028.www7.hp.com/ERC/downloads/59829141EN.pdf?jumpid=reg_R1002_USEN ) 6. Dynamic Logical Processors for Hyper-Threading on HP-UX 11i v3 (search http://docs.hp.
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ncores=4 #  When run in a vPar with 6 cores: # ./getnumcores ncores=6  When run in the same vPar with 6 cores, but configured with 2 FSS Groups (OTHERS and cputest), a 1 core PSET (pset1) and a 2 core PSET (pset2) here are the results. (The prmrun command was used to start the executable in each Resource Partition) : # prmrun ncores=3 # prmrun ncores=3 # prmrun ncores=1 # prmrun ncores=2 # -g OTHERS ./getnumcores -g cputest ./getnumcores -g pset1 ./getnumcores -g pset2 .
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activated (for example 16 cores in this example). Record the performance level when all the resources have been activated.  Run the procedure in reverse. Measure performance on a small static system (i.e. 4 cores in the example above), then measure performance on a system that starts large (16 cores) and scales down to the small size (4 cores).  Compare the results. An ideal application will deliver the same performance level in the dynamic VSE environment as in the static environment.