vmstat - Man Page
Report virtual memory statistics
Examples (TL;DR)
- Display virtual memory statistics:
vmstat - Display reports every 2 seconds for 5 times:
vmstat 2 5
Synopsis
vmstat [options] [delay [count]]
Description
vmstat reports information about processes, memory, paging, block IO, traps, disks and cpu activity.
The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length delay. The process and memory reports are instantaneous in either case.
Options
- delay
The delay between updates in seconds. If no delay is specified, only one report is printed with the average values since boot.
- count
Number of updates. In absence of count, when delay is defined, default is infinite.
- -a, --active
Display active and inactive memory, given a 2.5.41 kernel or better.
- -f, --forks
The -f switch displays the number of forks since boot. This includes the fork, vfork, and clone system calls, and is equivalent to the total number of tasks created. Each process is represented by one or more tasks, depending on thread usage. This display does not repeat.
- -m, --slabs
Displays slabinfo.
- -n, --one-header
Display the header only once rather than periodically.
- -s, --stats
Displays a table of various event counters and memory statistics. This display does not repeat.
- -d, --disk
Report disk statistics (2.5.70 or above required).
- -D, --disk-sum
Report some summary statistics about disk activity.
- -p, --partition device
Detailed statistics about partition (2.5.70 or above required).
- -S, --unit character
Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes. Note this does not change the swap (si/so) or block (bi/bo) fields.
- -t, --timestamp
Append timestamp to each line
- -w, --wide
Wide output mode (useful for systems with higher amount of memory, where the default output mode suffers from unwanted column breakage). The output is wider than 80 characters per line.
- -y, --no-first
Omits first report with statistics since system boot.
- -V, --version
Display version information and exit.
- -h, --help
Display help and exit.
Field Description for VM Mode
Procs
r: The number of runnable processes (running or waiting for run time). b: The number of processes blocked waiting for I/O to complete.
Memory
These are affected by the --unit option.
swpd: the amount of swap memory used. free: the amount of idle memory. buff: the amount of memory used as buffers. cache: the amount of memory used as cache. inact: the amount of inactive memory. (-a option) active: the amount of active memory. (-a option)
Swap
These are affected by the --unit option.
si: Amount of memory swapped in from disk (/s). so: Amount of memory swapped to disk (/s).
IO
bi: Kibibyte received from a block device (KiB/s). bo: Kibibyte sent to a block device (KiB/s).
System
in: The number of interrupts per second, including the clock. cs: The number of context switches per second.
Cpu
These are percentages of total CPU time.
us: Time spent running non-kernel code. (user time, including nice time) sy: Time spent running kernel code. (system time) id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time. wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle. st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown. gu: Time spent running KVM guest code (guest time, including guest nice).
Field Description for Disk Mode
Reads
total: Total reads completed successfully merged: grouped reads (resulting in one I/O) sectors: Sectors read successfully ms: milliseconds spent reading
Writes
total: Total writes completed successfully merged: grouped writes (resulting in one I/O) sectors: Sectors written successfully ms: milliseconds spent writing
IO
cur: I/O in progress s: seconds spent for I/O
Field Description for Disk Partition Mode
reads: Total number of reads issued to this partition read sectors: Total read sectors for partition writes : Total number of writes issued to this partition requested writes: Total number of write requests made for partition
Field Description for Slab Mode
Slab mode shows statistics per slab, for more information about this information see slabinfo(5)
cache: Cache name num: Number of currently active objects total: Total number of available objects size: Size of each object pages: Number of pages with at least one active object
Notes
vmstat requires read access to files under /proc. The -m requires read access to /proc/slabinfo which may not be available to standard users. Mount options for /proc such as subset=pid may also impact what is visible.
See Also
free(1), iostat(1), mpstat(1), ps(1), sar(1), top(1), slabinfo(5)
Reporting Bugs
Please send bug reports to procps@freelists.org
Referenced By
cifsiostat(1), cpupower-monitor(1), free(1), freecolor(1), iostat(1), mpstat(1), pidstat(1), pmrep(1), powerstat(8), sar(1), slabtop(1), smem(8), stress-ng(1), top(1), ttyplot(1), turbostat(8), vmtouch(8).