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vmstat(1)
NAME
vmstat - Displays virtual memory statistics
SYNOPSIS
vmstat interval [count]
vmstat [-D | -f | -i | -M | -p | -P | -r rad_id | -R | -s | -w]
The vmstat command displays system statistics for virtual memory,
processes, trap, and CPU activity.
OPTIONS
-D Displays debugging information if kmem_debug is set.
-f Displays only statistics about the number of forks since system startup
(see the fork() call).
-i Displays the following virtual memory statistics:
# vmstat -i
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr cpu
r w u act free wire fault cow zero react pin pout in sy cs us sy id
2 82 29 23K 12K 4906 3M 963K 834K 620 710K 0 73 30 391 0 2 98
-M Displays information about memory usage by buckets. This information
can be used for kernel debugging.
-p Displays statistics for the vm and ubc subsystems for all Resource
Affinity Domains (RADs). The following virtual memory (VM) information
is included in the display output:
VM faults All VM page faults.
VM kfaults Kernel page faults.
VM cowcopy Copy on write optimization missed, page copied.
VM kzfod Kernel zero filled on demand.
VM pagesteal
Page allocations resulting in a page steal.
VM prewrites
Total count of pre-written pages.
VM anon_prewrites
Count of prewritten anonymous object pages.
VM swap_prewrites
Count of prewritten swap object pages.
VM cleanrecs
Pages freed that are clean and reclaimable.
VM swaprecs Swap write reclaims.
VM lmsteal Page allocations resulting in a page steal.
VM lmstealwins
Page steal wins.
VM ffl Faults from the free list.
VM pout_scan
VM_pageout_scan calls.
VM pout_pagescan
VM_pageout_scan pages scanned.
VM pout_call
Pageout calls made.
VM pout Successful pageouts.
VM pout_target
Pageout target met.
VM pout_burst
Pageout I/O met.
VM act_scans
Active pages scanned while replenishing the least recently
used (LRU) list
VM act_moves
Active pages moved to the inactive list.
VM lock_fails
Failed loop lock tries during LRU processing.
VM migrations
Pages migrated to a new resource affinity domain (RAD).
VM TOT cowfaults
Total copy on write part of all faults.
VM TOT zfod Total user zero filled on demand.
VM TOT iowrites
Total I/O writes.
VM TOT pgwrites
Total page writes.
VM TOT ioreads
Total I/O reads.
VM TOT pgreads
Total page reads.
VM TOT reactivate
Total ages returned to the active list (reactivated).
The Unified Buffer Cache (UBC) data fields displayed when using the -p
option are as follows:
UBC allocscans
Page allocation resulting in a least recently used (LRU) scan.
UBC alloceol
The LRU scan has reached the end of list.
UBC allocpush
The number of LRU scan pushed pages.
UBC allocstole
The LRU scan stolen page allocation.
UBC allocseq
The number of page steal sequential drain attempts.
UBC wacalls
The number of LRU write ahead calls.
UBC wascans
The number of LRU write ahead scans.
UBC waeol
The LRU write ahead scan has hit the end of the list.
UBC prges
The number of LRU purge calls.
UBC prgscans
The number of LRU purge scans.
UBC prgeol
The LRU purge scan has hit the end of the list.
UBC prgburst
The LRU purge scan I/O target was met.
UBC prgfree
The number of LRU purge scan pages freed.
UBC mmapfree
The number of UBC mmaped pages freed.
UBC wdeny
The number of file system denied writes.
UBC hardsteals
The number of pagesteal required I/O and waits.
UBC stealscans
The number of pagesteal scans.
UBC dirtywra
The number of dirty write aheads.
UBC reclaim
The number of pages freed that are clean and reclaimable.
UBC pagesteal
The number of page allocations resulting in a page steal.
UBC lookups
The number of lookup tries.
UBC lookuphits
The number of lookup hits.
UBC ffl
The number of faults from the free list.
UBC lmsteal
The number of low memory steals
UBC lmstealwins
The number of low memory steal wins.
UBC seqdrain
The number of sequential drains.
UBC TOT alloc
The total memory demand on UBC.
UBC TOT reactivate
The total referenced LRU pages.
UBC TOT iowrites
The total I/O issued.
UBC TOT pgwrites
The total number of pages written.
-P Displays the following accumulated statistics about physical memory
use:
Total Physical Memory
Sum of the total physical memory in the machine.
Physical Memory Clusters
This statistic describes how physical memory is clustered. It
shows where memory is being used (pal, os, and nvram), the starting
and ending pageframes, and the total amount of memory used.
Physical Memory Use
This statistic shows a breakdown of physical memory used by the
operating system (such as text, data, and bss). It contains the
starting and ending pageframes, memory usage per category, and
total memory used.
Managed Pages Break Down
This statistic provides a snapshot of where managed physical memory
resides when the vmstat command was run. It indicates the number
of pages in the free, active, and inactive queues, the number of
wired pages, and the number of pages held in the unified buffer
cache (UBC).
WIRED Pages Break Down
This statistic describes the physical pages that are wired in
memory. The fields show the number of wired pages in anonymous (vm)
memory, the UBC, pages used for meta data, the kernel malloc pools,
contiguous memory, and pages used for page table entries (ptes).
The display typically shows:
· vm and ubc wired pages
· meta data, malloc, and contig pages
· user, kernel, and free ptepages
-r rad_id
Displays virtual memory statistics for the specified Resource Affinity
Domain (RAD) only. The rad_id is an integer assigned automatically by
the system.
Process (procs) data fields displayed when you use the -r option are as
follows:
· RAD - Resource Affinity Domain identifier (integer)
· r - Number of threads that are running or are runnable
· w - Number of threads that can be interrupted that are waiting
· u - Number of threads that cannot be interrupted that are waiting
· st - Number of stopped threads
· sw - Number of swapped threads
Memory data fields displayed when you use the -r option are as follows:
· actv - Total number of pages on the active list.
· actu - Number of active vm pages.
· acti - Number of inactive vm pages.
· free - Total number of pages that are clean and available for use.
· wire - Total number of wired pages.
· wirv - Number of wired vm pages.
· wiru - Number of wired UBC pages.
Because of a restriction on the display space, the contents of some
fields are truncated rather than rounded up.
-R Displays information for all RADs. Typical output is shown under the -r
option.
-s Displays the following accumulated statistics along with the page size:
active pages
Total number of pages that are currently in use but can be used for
paging.
inactive pages
Total number of VM pages that are allocated but are most likely to
be used for paging.
free pages
Total number of unreferenced (clean) pages that are available for
use.
wired pages
Total number of pages that are currently in use and cannot be used
for paging (not a real list).
virtual memory page faults
Number of address translation faults that have occurred.
copy-on-write page faults
Number of copy-on-write page faults, which occur if the requested
page is shared by a parent process and one or more child processes
(using the fork function), and if one of the processes needs to
modify the page. In this case, VM loads a new address into the
translation buffer and copies the contents of the requested page
into the new address for modification by the process.
zero file page faults
Number of zero-filled-on-demand page faults, which occur if VM
cannot find the page in the internal data structures and if the
requested page is new and has never been referenced. In this case,
VM initializes a physical page (the contents of the page are zeroed
out) and loads the address into the page table.
reattaches from reclaim list
Number of pages that have been faulted while on the inactive list.
pages paged in
Number of requests for pages from a pager.
pages paged out
Number of pages that have been paged out.
task and thread context switches
Number of task and thread context switches.
device interrupts
Number of nonclock device interrupts.
system calls
Number of system calls called.
-w Appends iowait information to the default output as follows:
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr cpu
r w u act free wire fault cow pin pout in sy cs us sy id iowait
2 82 29 23K 12K 4905 3M 963K 710K 0 73 30 391 0 2 98 0
DESCRIPTION
Use the vmstat command to display statistics which describe how virtual
memory is used.
To cause the vmstat command to display statistics at the specified
interval, specify a time in seconds for the optional interval parameter.
The first report generated by the vmstat command includes statistics for
the time since the last reboot. Each subsequent report is for the
specified interval only. To control the number of reports generated,
specify a value for the count parameter after the interval parameter.
For example, the command vmstat 1 10 produces 10 reports at 1-second
intervals. You cannot specify a value for the count parameter without also
specifying a value for the interval parameter because the first numeric
argument to vmstat is always assumed to be interval.
At any time, system memory can be in use by the kernel as follows:
· kseg -- In use by kseg
· UBC - In use by the unified buffer cache
· wired - Pages that are currently in use and cannot be used for paging
· On the active list - Pages that are currently in use but can be used
for paging
· On the inactive list - Pages that are allocated but are most likely to
be used for paging
· On the free list - Pages that are clean and available for use
The vmstat command does not report on the memory in kseg and memory used by
the UBC.
The following values are displayed:
Process information:
r Number of threads that are running or are runnable.
w Number of threads waiting interruptibly.
u Number of threads waiting uninterruptibly.
Virtual memory information:
act Total number of pages on the active list, the inactive list (pages that
are allocated but are most likely to be used for paging), and UBC least
recently used (LRU) list.
free
Total number of pages that are clean and available for use.
wire
Total number of pages that are currently in use and cannot be used for
paging (not a real list).
fault
Number of address translation faults that have occurred.
cow Number of copy-on-write page faults, which occur if the requested page
is shared by a parent process and one or more child processes (using
the fork function) and if one of the processes needs to modify the
page. In this case, VM loads a new address into the translation buffer
and copies the contents of the requested page into the new address for
modification by the process.
zero
Number of zero-filled-on-demand page faults, which occur if VM cannot
find the page in the internal data structures and if the requested page
is new and has never been referenced. In this case, VM initializes a
physical page (the contents of the page are zeroed out) and loads the
address into the page table.
react
Number of pages that have been faulted while on the inactive list.
pin Number of requests for pages from a pager.
pout
Number of pages that have been paged out.
Interrupt information:
in Number of nonclock device interrupts per second.
sy Number of system calls called per second.
cs Number of task and thread context switches per second.
CPU information:
us Percentage of user time for normal and priority processes.
sy Percentage of system time.
id Percentage of idle time.
iowait
Percentage of iowait. If the -w option is not specified, the iowait
time is included in the id statistic.
Specify -f to display fork statistics only. Specify -s for a single
display of accumulated statistics, as well as page size.
EXAMPLES
1. The following is an example of the typical output (derived from a
single-RAD, single-CPU server) when using the -p option:
# vmstat -p
Total RADs: 1 Total CPUs: 1 Total Ticks: 512
36441297 VM faults 1677 VM kfaults
2115850 VM cowcopy 1677 VM kzfod
0 VM pagesteal 0 VM prewrites
0 VM anon_prewrites 0 VM swap_prewrites
0 VM cleanrecs 0 VM swaprecs
0 VM lmsteal 0 VM lmstealwins
0 VM ffl 0 VM pout_scan
0 VM pout_pagescan 0 VM pout_call
0 VM pout 0 VM pout_target
0 VM pout_burst 12548 VM act_scans
12548 VM act_moves 0 VM lock_fails
0 VM migrations
2547665 VM TOT cowfaults 3813949 VM TOT zfod
0 VM TOT iowrites 0 VM TOT pgwrites
26823910 VM TOT ioreads 0 VM TOT pgreads
1423 VM TOT reactivate
0 UBC allocscans 0 UBC alloceol
0 UBC allocpush 0 UBC allocstole
0 UBC allocseq 0 UBC wacalls
0 UBC wascans 0 UBC waeol
0 UBC prges 0 UBC prgscans
0 UBC prgeol 0 UBC prgburst
0 UBC prgfree 0 UBC mmapfree
79566 UBC wdeny 0 UBC hardsteals
0 UBC stealscans 0 UBC dirtywra
0 UBC reclaim 0 UBC pagesteal
42127497 UBC lookups 41985615 UBC lookuphits
0 UBC ffl 0 UBC lmsteal
0 UBC lmstealwins 0 UBC seqdrain
144957 UBC TOT alloc 0 UBC TOT iowrites
0 UBC TOT reactivate 0 UBC TOT pgwrites
2. The following is an example of typical output (reformatted for ease of
reference) when you use the -r option:
# vmstat -r 0
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages
RAD r w u st sw act actv actu acti free wire wirv wiru fault
0 2 157 27 0 0 31K 4928 18K 8813 24K 6544 3015 0 36M
intr cpu
cow zero react pin pout in sy cs us sy id
2M 3M 1423 26M 0 102 249 229 0 1 99
SEE ALSO
Commands: iostat(1), sysman(8)
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