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HP-UX Virtual Partitions Administrator’s Guide > Chapter 7 CPU, Memory, and I/O Resources (A.04.xx)

Granularity Issues (Integrity and PA-RISC)

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CAUTION: (vparcreate only) When you specify the granularity value for only one type of memory (ILM or CLM), the granularity value for the other type of memory is set using the default granularity value. For example, if you specify only -g ILM:256, the -g CLM:128 is implied where 128 is the vPars default granularity value.

If your system (or nPartition) contains a large amount of memory (32 GB or more), you should set the granularity value to the largest amount possible to reduce the total boot time (relative to boot time in nPars/standalone) caused by the initial hardware scanning of memory. For CLM on PA-RISC platforms and for both ILM and CLM on Integrity platforms, you should choose the largest possible granularity value.

However, you should be careful when using the granularity option; using the option incorrectly can cause all the virtual partitions to not be bootable.

Further, granularity in the vPars database can only be specified during the creation of the vPars database. This means the first vparcreate command performed to create the database can be used to specify the granularity, but it cannot be changed after that. It cannot be changed by subsequent vparcreate commands nor any other commands; any change in values requires the entire vPars database to be re-created. Therefore, read this section thoroughly.

For details on granularity values and granularity limitations, see the vparresources(5) manpage. The granularity section of this manpage is provided below since there are critical notes in the manpage of which you should know when planning a granularity value. These include:

  • The minimum value for granularity of both ILM and CLM is 64 MB.

  • The chosen granularity value(s) must be an integral power of 2 (in other words, 2^X).

  • (Integrity only) There is a limit on the number of CLM granules per cell and total ILM granules you can set. Use the vparenv command to see the maximum possible granules for ILM and CLM for your specific system. For example:

    # vparenv vparenv: The next boot mode setting is "vPars". vparenv: The ILM granule size setting is 128. vparenv: The CLM granule size setting is 128. vparenv: Note: Any changes in the above settings will become effective only after the next system reboot. vparenv: Note: The maximum possible CLM granules per cell is 64. vparenv: Note: The maximum possible ILM granules for this system is 1024.

    If either of these values are exceeded when you set your granularity values, the vPars Monitor will not boot any virtual partitions. You must rebuild your vPars database such that the number of granules related to both ILM and CLM do not exceed the numbers in your vparenv output.

  • (PA-RISC only) Excluding the first granule, a portion of which is used by the vPars Monitor, there must be at least one entire granule that exists below the 2 GB limit for each virtual partition. These granules below the 2 GB limit are used by kernel of each virtual partition.

  • Especially for nPartitions or systems containing 32 GB or more of total memory, you should set the granule to the highest possible granule size to reduce the time in scanning the memory during the initial hardware boot.

  • (Integrity only) In order for the virtual partitions in an active database to be able to boot, the granularity values in the vPars database must match those written in the system firmware.

Granularity described in vparresources(5)

For reference, below is the granularity section of the manpage vparresources(5):

Granularity Memory is normally assigned to vPars in units called granules. Exceptions are described below. The granule values for CLM and ILM can be different. However, both are subject to the following rules: + MOST IMPORTANT, READ CAREFULLY. Granularity, the value of a granule specification, is not a resource. Resource assignments can be modified, even if some resource modifications require that a vPar be Down. Granularity can only be specified when creating a new database. It cannot be changed thereafter. + The minimum values (ILM and CLM) are 64 MB. + The default values are 128 MB. + The recommended specifications are described below. + Any chosen granularity must be an integral power of 2, not just a multiple of 64. For example, 256 is a legal value, but 192 is not. + Although a granularity must be an integral power of 2, memory can be assigned in any multiple of that value. For example, if the CLM granularity is 128 MB, it is legal to assign 384 MB of CLM to a vPar. + Integrity systems have a platform-dependent limit to the number of CLM granules per cell or ILM granules that may be configured. You can determine specific limits for your installation by using the vparenv command and examining the "The maximum possible xLM granules..." messages. Note: When in nPar mode, the vparenv command does not display the "The maximum possible xLM granules..." messages if the next boot mode setting is nPars. So in order to get these values, you have to first change the next boot mode setting to vPars (reboot not required) and then invoke the vparenv command. These values, combined with your total memory of each type, determine the minimum granularities you should specify in order to allow your vPars to boot. For example, if you are allowed 1024 ILM granules and your total memory is <= 128 GB, you can use the default ILM granularity of 128 MB. Or if you are allowed 16 CLM granules per cell, and your nPar configuration includes two cells each configured with 8 GB of CLM, your CLM granularity must be >= 512 MB. If the total ILM memory or CLM memory per cell exceeds that which can be configured in the maximum number of granules using your specified granularity, the vPar Monitor will not boot any vPar. In this case, you must increase one or both granularities appropriately so that all available memory can be accommodated. This will require a complete reconfiguration of your database. Careful configuration planning will avoid this situation. Granularity limitations do not apply to PA-RISC platforms. However, there are guidelines that do apply to both PA-RISC and Integrity systems. These are described next. + Recommendations for ILM and CLM granularity specifications: On PA-RISC platforms, each vPar needs ILM below 2 GB to load and launch its kernel. However, portions of the first granule (starting at address 0) are used for the Monitor's code and data, therefore will not be used for the kernel. Hence, excluding the first granule, there should be at least one granule below 2 GB for each partition. So if ILM granularity is 128 MB, the first 2 GB will consist of 16 granules. Therefore, it will be possible to load and launch the maximum supported 8 vPars. If ILM granularity is 256 MB, there are only 8 granules in the first 2 GB. The Monitor uses portions of the first one. So it will only be possible to load and launch 7 or fewer vPars. On ab Integrity server, there is no similar constraint on the maximum ILM granularity. For CLM on PA-RISC platforms, and for both ILM and CLM on Integrity systems, Hewlett-Packard recommends choosing the largest possible granularity for performance reasons. The granularity can be such that it is equal to the partition with the least amount of that memory type. For example, if the system contains 64 GB of ILM and the smallest ILM specification of any vPar is 1 GB, then ILM granularity can be 1 GB. If the system contains 64 GB of CLM per cell and the smallest CLM specification from any cell of any vPar is 4 GB, the CLM granularity can be 4 GB. + For an Integrity server, the chosen granularity values must also be written to system firmware storage. When the Monitor is started and a vPar database is loaded, the values in the database must match those in firmware, or the Monitor will not allow the database to be used. While in nPars mode, you should use the vparstatus and vparenv commands to verify that the database and firmware granularities are identical. If not, you must either create a new database with the correct granularities using the vparcreate -g command, or change the firmware granularities with the vparenv -g command. Although memory is normally allocated in integral granules, some memory ranges are withheld for use by the Monitor or by firmware. The vparstatus -m command displays these ranges. Other ranges of address space are simply non-existent. Because of this fragmentation, the Monitor may assign your vPar slightly more or less than an integral granule of memory when the vPar boots.
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