Content-type: text/html Man page of vmstat

vmstat

Section: User Commands (1)
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NAME

vmstat - Displays virtual memory statistics  

SYNOPSIS

vmstat interval [count]

vmstat [-f|-M|-P|-s]

The vmstat command displays system statistics for virtual memory, processes, trap, and CPU activity.
 

OPTIONS

Displays only statistics about the number of forks since system startup (see the fork() call). Displays information about memory usage by buckets. This information can be used for kernel debugging. Displays the following accumulated statistics about physical memory use: Number of megabytes of installed memory, and the equivalent page value. How physical memory is clustered. The starting and ending page frames (pfn) and where the memory is utilized (pal, os, and *nvram). A breakdown of memory usage by os, the starting and ending page frames, type of usage such as unixtable, or bss and the total physical memory in use. A snapshot of where managed physical memory resided when the vmstat command executed. The display shows the number of pages in the free queue, active and inactive pages, wired pages and unified buffer cache (ubc) pages. A further breakdown of physical pages that are wired in memory. The display typically shows: vm and ubc wired pages meta data, malloc, and contig pages user, kernel, and free ptepages. Displays the following accumulated statistics along with the page size: Total number of pages that are currently in use but can be used for paging. Total number of VM pages that are allocated but are most likely to be used for paging. Total number of unreferenced (clean) pages that are available for use. Total number of pages that are currently in use and cannot be used for paging (not a real list). Number of address translation faults that have occurred. 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. 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. Number of pages that have been faulted while on the inactive list. Number of requests for pages from a pager. Number of pages that have been paged out. Number of task and thread context switches per second. Number of nonclock device interrupts per second. Number of system calls called per second.
 

DESCRIPTION

If you specify interval, vmstat displays the statistics listed below every interval seconds. The first report is for all time since a reboot, and each subsequent report is for the last interval only. If you specify count after interval, count specifies the number of reports. For example, vmstat 1 10 produces 10 reports at 1-second intervals. You cannot specify count without interval, since the first numeric argument to vmstat is always assumed to be interval.

At any time, system memory can be in use by the kernel in kseg, 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), or used by the Unified Buffer Cache (UBC). The vmstat command does not report on the memory in kseg and memory used by the UBC.

The following values are displayed:

Process information: Number of threads that are running or are runnable. Number of threads waiting interruptibly. Number of threads waiting uninterruptibly.

Virtual memory information: 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 the Unified Buffer Cache (UBC) least recently used (LRU) list. Total number of pages that are clean and available for use. Total number of pages that are currently in use and cannot be used for paging (not a real list). Number of address translation faults that have occurred. 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. 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. Number of pages that have been faulted while on the inactive list. Number of requests for pages from a pager. Number of pages that have been paged out.

Interrupt information: Number of nonclock device interrupts per second. Number of system calls called per second. Number of task and thread context switches per second.

CPU information: Percentage of user time for normal and priority processes. Percentage of system time. Percentage of idle time.

Specify -f to display fork statistics only. Specify -s for a single display of accumulated statistics, as well as page size.
 

SEE ALSO

Commands:  iostat(1)


 

Index

NAME
SYNOPSIS
OPTIONS
DESCRIPTION
SEE ALSO

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Time: 02:42:44 GMT, October 02, 2010