Commands Reference, Volume 6

vmtune Command

Purpose

Compatibility script to set parameters of the Virtual Memory Manager and other AIX components.

Syntax

vmtune [ -a ]

vmtune [ -M Number ] [ -p Number ] [ -P Number ] [ -t Number ] [ -f Number ] [ -F Number ] [ -l Number ] [ -r Number ] [ -R Number ] [ -N Number ] [ -w Number ] [ -W Number] [ -k Number ] [ -c Number ] [ -b Number] [ -B Number ] [ -u Number] [ -d 0|1 ] [ -s 0|1 ] [ -S 0|1 ] [ -L Number ] [ -g Number ] [ -h 0|1 ] [ -m Number ] [ -C 0|1 ] [ -v Number ] [ -n Number ] [ -j Number] [ -J Number ] [ -z Number] [ -Z Number] [ -q Number ] [ -Q Number ] [ -V Number] [ -i Number ] [ -y 0|1 ] [ -T Number ]

Description

The vmtune sample program is being phased out and is not supported in future releases. It is replaced with the vmo command (for all the pure VMM parameters) and the ioo command (for all the I/O related parameters) which can be used to set most of the parameters that were previously set by vmtune. The -v flag has been added to vmstat to replace the -A flag which display counter values instead of tuning parameters. For AIX 5.2, a compatibility script calling vmo and ioo is provided to help the transition.

The vmtune command can only be executed by root. Changes made by the vmtune command last until the next reboot of the system. In AIX 5.2, vmo and ioo can be used to make changes permanent and to change parameters needing the execution of bosboot and/or rebooting to be effective.

Attention: Misuse of this script can cause performance degradation or operating-system failure. Be sure that you have studied the appropriate tuning sections of the Performance Mangement Guide before using vmtune to change system parameters.

Flags

Note

If no flags are specified, vmo -a and ioo -a are called to display the current values.

-a	Calls vmo -a and ioo -a to display the current values for all parameters.
-A	Calls vmstat -v to display the current statistic counters.
-b Number	Calls ioo -o numfsbuf=Number to set the number of file systems bufstructs.
-B Number	Calls ioo -o hd_pbuf_cnt=Number to set the number of pbufs used by the LVM.
-c Number	Calls ioo -o numclust=Number to set the number of 16 KB clusters processed by write behind.
-C 0\|1	Accepted, but not directly supported. Use vmo -r -o pagecoloring= 0\|1 to disable/enable page coloring for specific hardware platforms.
-d 0\|1	Calls vmo -o deffps=0\|1 to turn on and off deferred paging space allocation.
-fNumber	Calls vmo -o minfree=Number to set the number of frames on the free list.
-F Number	Calls vmo -o maxfree=Number to set the number of frames on the free list at which stealing is to stop.
-g Number	Accepted, but not directly supported. Use vmo -r -o lgpg_size Number -o lgpg_regions=NumberRegions to set the size, in bytes, of the hardware-supported large pages.
-h 0\|1	Calls vmo -o strict_maxperm=0\|1 to specify whether maxperm% should be hard limit.
-i Number	Accepted, but not directly supported. Use vmo -r -o spec_dataseg_int= Number to set the interval to use when reserving the special data seg identifiers.
-j Number	Calls ioo -o j2_nPagesPerWriteBehindCluster=Number to set the number of pages per write-behind cluster.
-J Number	Calls ioo -o j2_maxRandomWrite=Number to set the random-write threshold count.
-k Number	Calls vmo -o npskill=Number to set the number of paging space pages at which processes begin to be killed.
-l Number	Calls vmo -o lruBucket=Number to set the size of the least recently used page replacement bucket size.
-L Number	Accepted, but not directly supported. Use vmo -r -o lgpg_Region= Number -o lgpg_size=Size to set the number of large pages to be reserved.
-m Number	Accepted, but not directly supported. Use vmo -r -o memorypools=Number to set the number of memory pools.
-M Number	Calls vmo -omaxpin=Number to set the maximum percentage of real memory that can be pinned.
-n Number	Calls vmo -o nokilluid=Number to specify the uid range of processes that should not be killed when paging space is low.
-N Number	Calls ioo -o pd_npages=Number to set the number of pages that should be deleted in one chunk from RAM when a file is deleted.
-p Number	Calls vmo -o minperm%=Number to set the point below which file pages are protected from the repage algorithm.
-P Number	Calls vmo -o maxperm%=Number to set the point above which the page stealing algorithm steals only file pages.
-q Number	Calls ioo -o j2_minPageReadAhead=Number to set the minimum number of pages to read ahead.
-Q Number	Calls ioo -o j2_maxPageReadAhead=Number to set the maximum number of pages to read ahead.
-r Number	Calls ioo -o minpageahead=Number to set the number of pages with which sequential read-ahead starts.
-R Number	Calls ioo -o maxpageahead=Number to set the minimum number of pages to be read ahead.
-s 0\|1	Calls ioo -o sync_release_illock=0\|1 to enable the code that minimizes the time spent holding inode lock during sync.
-S 0\|1	Calls vmo -o v_pinshm=0\|1 to enable the SHM_PIN flag on the shmget system call.
-t Number	Calls vmo -o maxclient%=Number to set the point above which the page stealing algorith steals only client file pages.
-T Number	Calls vmo -o pta_balance_threshold=Number to set the point at which a new pta segment will be alocated.
-u Number	Calls vmo -o lvm_bufcnt=Number to set the number of LVM buffers for raw physical I/Os.
-v Number	Accepted, but not directly supported. Use vmo -r -o framesets= Number to set the number of framesets per mempool.
-V Number	Accepted, but not directly supported. Use vmo -r -o num_spec_dataseq= Number to set the number of reserved special data segment IDs.
-w Number	Calls vmo -o npswarn=Number to set a threshold for random writes to accumulate in RAM before pages are sync'd to disk using a write-behind algorithm.
-W Number	Calls ioo -o maxrandwrt=Number to set the number of free paging-space pages at which SIGDANGER is sent to processes.
-y 0\|1	Accepted, but not directly supported. Use vmo -r -o Memory_Affinity=0\|1 to enable memory affinity on sertain hardware.
-z Number	Calls ioo -o j2_nRandonCluster=Number to set random write threshold distance.
-Z Number	Calls ioo -o j2_nBufferPerPagerDevice=Number to set the number of buffers per pager device.
-?	Displays a description of the command and its flags.

See the Tunable Parameters sections of the vmo command and the ioo command for more details about tunable parameters.

Related Information

The vmo command, ioo command.

Modifications to vmtune and schedtune in AIX 5L Version 5.2 Performance Management Guide.

The Kernel Tuning section in AIX 5L Version 5.2 Performance Tools Guide and Reference.

Performance Overview of the Virtual Memory Manager (VMM)