vparresources.5 (2010 09)

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Granularity

Memory is normally assigned to virtual partitions 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. Refer to the section

Default memory granularity in

A.05.01 for Itanium-based platforms for more details.

• 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.

• There is a limit on the number of granules speciﬁed on the command line for online memory

addition/deletion. In such cases the user can retry with lesser options/granules on the command line.

• Itanium-based platforms 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. These

values, combined with your total memory of each type, determine the minimum granularities you

should specify in order to allow your virtual partitions 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 nPartition 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 max-

imum 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 Itanium-based platforms. 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, por-

tions 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 virtual parti-

tions. 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 virtual partitions.

On Itanium-based platforms, there is no similar constraint on the maximum ILM granularity.

• For an Itanium-based platform, 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 nPar 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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