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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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VMSTAT(8) System Manager's Manual VMSTAT(8)
vmstat - Report virtual memory statistics
vmstat [option ...] [delay [count]]
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.
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 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.
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).
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
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
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
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.
free(1), iostat(1), mpstat(1), ps(1), sar(1), top(1), slabinfo(5)
Please send bug reports to ⟨procps@freelists.org⟩.
This page is part of the procps-ng (/proc filesystem utilities)
project. Information about the project can be found at
⟨https://gitlab.com/procps-ng/procps⟩. If you have a bug report
for this manual page, see
⟨https://gitlab.com/procps-ng/procps/blob/master/Documentation/bugs.md⟩.
This page was obtained from the project's upstream Git repository
⟨https://gitlab.com/procps-ng/procps.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-07-30.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
procps-ng 2024-07-19 VMSTAT(8)
Pages that refer to this page: cifsiostat(1), free(1), iostat(1), mpstat(1), pidstat(1), pmrep(1), sar(1), slabtop(1), top(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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