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Changing the tunable values using vxtune

You can use vxtune to display, set, or change the memory tunables that are used by VVR. The advantage of using the vxtune utility to tune the parameters is that you need not reboot the system after modifying the tunable value.

The vxtune utility allows you to use suffixes of K or M to specify values, and enables you to modify the values of the following memory tunables:

vol_rvio_maxpool_sz

vol_min_lowmem_sz

vol_max_rdback_sz

vol_max_nmpool_sz

vol_max_wrspool_sz

These tunable values are then updated in the /etc/vx/vxtunables file.

You can enable auto-tuning for the vol_min_lowmem_sz tunable by setting the tunable value to -1. However, if you do not want it to be auto-tuned then you must set it to a required value. Auto-tuning is only supported for the tunable vol_min_lowmem_sz.

 To display the tunables that vxtune supports

Issue the following command on the required system to display the tunables that VVR supports along with their current values and brief description:

# vxtune

The output of this command resembles:

Tunable Value Description

----------------- -------- ---------------

vol_rvio_maxpool_sz 102325 RVIO Pool Size (KBytes)

vol_min_lowmem_sz 528 Low Memory Threshold (KBytes)

vol_max_rdback_sz 65536 Readback Pool Size (KBytes)

vol_max_nmpool_sz 16384 NMCOM Pool Size (KBytes)

vol_max_wrspool_sz 16384 WriteShippingPoolSize(KBytes)

volpagemod_max_memsz 6144 Cache SizeFMRMetadata(KBytes)

  Note   The default unit for value is bytes and default display value of the tunables is in kilobytes (K).

To display the output in bytes, use the vxtune command with the -r option as follows

# vxtune -r

The output resembles:

Tunable Value Description

----------------- -------- ---------------

vol_rvio_maxpool_sz 104780185 RVIO Pool Size (Bytes)

vol_min_lowmem_sz 540672 Low Memory Threshold (Bytes)

vol_max_rdback_sz 67108864 Readback Pool Size (Bytes)

vol_max_nmpool_sz 16777216 NMCOM Pool Size (Bytes)

vol_max_wrspool_sz 16777216 Write ShippingPoolSize(Bytes)

 To display the values of specific tunables

Use the following command on the required host to display the value of the specific tunable:

# vxtune tunable_name

This command displays the value of the specified tunable in kilobytes (K).

To display the output in bytes, use the vxtune command with the -r option.

# vxtune -r tunable_name

For example, to view the value of the tunable vol_rvio_maxpool_sz, use the following command:

# vxtune vol_rvio_maxpool_sz

The output resembles:

65536(K)

 To modify the values of the tunables

Use the following command on the required host to modify the value of the specific tunable:

# vxtune tunable_name value

The value value of the tunable can be specified in units of K, MB, or GB. However, the value is always displayed in kilobytes (K) regardless of the units that you have specified it in. For example, if you specify a value 500MB the value will be automatically converted and will be displayed as 512000K. You can use the command with the -r option to display the value in bytes.

For example, to change the default value of the vol_rvio_maxpool_sz tunable to 128MB, use the following command.

# vxtune vol_rvio_maxpool_sz 128M

To view the changed value for the tunable use the following command

# vxtune vol_rvio_maxpool_sz

  Caution   Do not edit the tunable values directly in the vxtunables file because these changes will be ignored.