.\" .\" Copyright (c) 2002-2023 Craig Small .\" Copyright (c) 2012-2023 Jim Warner .\" Copyright (c) 2011-2012 Sami Kerola .\" Copyright (c) 1994 Henry Ware .\" .\" This program is free software; you can redistribute it and/or modify .\" it under the terms of the GNU General Public License as published by .\" the Free Software Foundation; either version 2 of the License, or .\" (at your option) any later version. .\" .\" .TH VMSTAT 8 "2023-01-18" "procps-ng" "System Administration" .SH NAME vmstat \- Report virtual memory statistics .SH SYNOPSIS .B vmstat [options] .RI [ delay " [" count ]] .SH DESCRIPTION .B vmstat reports information about processes, memory, paging, block IO, traps, disks and cpu activity. .PP The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length .IR delay . The process and memory reports are instantaneous in either case. .SH OPTIONS .TP .I delay The .I delay between updates in seconds. If no .I delay is specified, only one report is printed with the average values since boot. .TP .I count Number of updates. In absence of .IR count , when .I delay is defined, default is infinite. .TP \fB\-a\fR, \fB\-\-active\fR Display active and inactive memory, given a 2.5.41 kernel or better. .TP \fB\-f\fR, \fB\-\-forks\fR The .B \-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. .TP \fB\-m\fR, \fB\-\-slabs\fR Displays slabinfo. .TP \fB\-n\fR, \fB\-\-one-header\fR Display the header only once rather than periodically. .TP \fB\-s\fR, \fB\-\-stats\fR Displays a table of various event counters and memory statistics. This display does not repeat. .TP \fB\-d\fR, \fB\-\-disk\fR Report disk statistics (2.5.70 or above required). .TP \fB\-D\fR, \fB\-\-disk-sum\fR Report some summary statistics about disk activity. .TP \fB\-p\fR, \fB\-\-partition\fR \fIdevice\fR Detailed statistics about partition (2.5.70 or above required). .TP \fB\-S\fR, \fB\-\-unit\fR \fIcharacter\fR Switches outputs between 1000 .RI ( k ), 1024 .RI ( K ), 1000000 .RI ( m ), or 1048576 .RI ( M ) bytes. Note this does not change the swap (si/so) or block (bi/bo) fields. .TP \fB\-t\fR, \fB\-\-timestamp\fR Append timestamp to each line .TP \fB\-w\fR, \fB\-\-wide\fR 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. .TP \fB\-y\fR, \fB\-\-no-first\fR Omits first report with statistics since system boot. .TP \fB\-V\fR, \fB\-\-version\fR Display version information and exit. .TP \fB\-h\fR, \fB\-\-help\fR Display help and exit. .PD .SH FIELD DESCRIPTION FOR VM MODE .SS Procs .nf r: The number of runnable processes (running or waiting for run time). b: The number of processes blocked waiting for I/O to complete. .fi .SS Memory These are affected by the \fB\-\-unit\fR option. .nf 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. (\fB\-a\fR option) active: the amount of active memory. (\fB\-a\fR option) .fi .SS Swap These are affected by the \fB\-\-unit\fR option. .nf si: Amount of memory swapped in from disk (/s). so: Amount of memory swapped to disk (/s). .fi .SS IO .nf bi: Kibibyte received from a block device (KiB/s). bo: Kibibyte sent to a block device (KiB/s). .fi .SS System .nf in: The number of interrupts per second, including the clock. cs: The number of context switches per second. .fi .SS CPU These are percentages of total CPU time. .nf 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). .fi .SH FIELD DESCRIPTION FOR DISK MODE .SS Reads .nf total: Total reads completed successfully merged: grouped reads (resulting in one I/O) sectors: Sectors read successfully ms: milliseconds spent reading .fi .SS Writes .nf total: Total writes completed successfully merged: grouped writes (resulting in one I/O) sectors: Sectors written successfully ms: milliseconds spent writing .fi .SS IO .nf cur: I/O in progress s: seconds spent for I/O .fi .SH FIELD DESCRIPTION FOR DISK PARTITION MODE .nf 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 .fi .SH FIELD DESCRIPTION FOR SLAB MODE Slab mode shows statistics per slab, for more information about this information see .BR slabinfo (5) .PP .nf 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 .fi .SH NOTES .B vmstat requires read access to files under \fI/proc\fR. The \fB\-m\fR requires read access to \fI/proc/slabinfo\fR which may not be available to standard users. Mount options for \fI/proc\fR such as \fIsubset=pid\fR may also impact what is visible. .SH "SEE ALSO" .BR free (1), .BR iostat (1), .BR mpstat (1), .BR ps (1), .BR sar (1), .BR top (1), .BR slabinfo (5) .SH "REPORTING BUGS" Please send bug reports to .UR procps@freelists.org .UE