Friday, May 17, 2013



The first line of vmstat represents a summary of information since boot time. To obtain useful real-time statistics, run vmstat with a time step (eg vmstat 30).

The vmstat output columns are as follows use the pagesize command to determine the size of the pages):

  • procs or kthr/r: Run queue length.
  • procs or kthr/b: Processes blocked while waiting for I/O.
  • procs or kthr/w: Idle processes which have been swapped.
  • memory/swap: Free, unreserved swap space (Kb).
  • memory/free: Free memory (Kb). (Note that this will grow until it reaches lotsfree, at which point the page scanner is started. See "Paging" for more details.)
  • page/re: Pages reclaimed from the free list. (If a page on the free list still contains data needed for a new request, it can be remapped.)
  • page/mf: Minor faults (page in memory, but not mapped). (If the page is still in memory, a minor fault remaps the page. It is comparable to the vflts value reported by sar -p.)
  • page/pi: Paged in from swap (Kb/s). (When a page is brought back from the swap device, the process will stop execution and wait. This may affect performance.)
  • page/po: Paged out to swap (Kb/s). (The page has been written and freed. This can be the result of activity by the pageout scanner, a file close, or fsflush.)
  • page/fr: Freed or destroyed (Kb/s). (This column reports the activity of the page scanner.)
  • page/de: Freed after writes (Kb/s). (These pages have been freed due to a pageout.)
  • page/sr: Scan rate (pages). Note that this number is not reported as a "rate," but as a total number of pages scanned.
  • disk/s#: Disk activity for disk # (I/O's per second).
  • faults/in: Interrupts (per second).
  • faults/sy: System calls (per second).
  • faults/cs: Context switches (per second).
  • cpu/us: User CPU time (%).
  • cpu/sy: Kernel CPU time (%).
  • cpu/id: Idle + I/O wait CPU time (%).

vmstat -i reports on hardware interrupts.

vmstat -s provides a summary of memory statistics, including statistics related to the DNLC, inode and rnode caches.

vmstat -S reports on swap-related statistics such as:

  • si: Swapped in (Kb/s).
  • so: Swap outs (Kb/s).

(Note that the man page for vmstat -s incorrectly describes the swap queue length. In Solaris 2, the swap queue length is the number of idle swapped-out processes. (In SunOS 4, this referred to the number of active swapped-out processes.)

Solaris 8

vmstat under Solaris 8 will report different statistics than would be expected under an earlier version of Solaris due to a different paging algorithm:
  • Page Reclaim rate higher.
  • Higher reported Free Memory: A large component of the filesystem cache is reported as free memory.
  • Low Scan Rates: Scan rates will be near zero unless there is a systemwide shortage of available memory.

vmstat -p reports paging activity details for applications (executables), data (anonymous) and filesystem activity.

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