{
    "mode": "man",
    "parameter": "VMSTAT",
    "section": "8",
    "url": "https://www.chedong.com/phpMan.php/man/VMSTAT/8/json",
    "generated": "2026-06-11T21:25:08Z",
    "synopsis": "vmstat [options] [delay [count]]",
    "sections": {
        "NAME": {
            "content": "vmstat - Report virtual memory statistics\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "vmstat [options] [delay [count]]\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "vmstat  reports  information  about processes, memory, paging, block IO, traps, disks and cpu\nactivity.\n\nThe first report produced gives averages since the last reboot.  Additional reports give  in‐\nformation on a sampling period of length delay.  The process and memory reports are instanta‐\nneous in either case.\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "delay  The delay between updates in seconds.  If no delay is specified, only  one  report  is\nprinted with the average values since boot.\n\ncount  Number of updates.  In absence of count, when delay is defined, default is infinite.\n",
            "subsections": [
                {
                    "name": "-a --active",
                    "content": "Display active and  inactive memory, given a 2.5.41 kernel or better.\n",
                    "flag": "-a",
                    "long": "--active"
                },
                {
                    "name": "-f --forks",
                    "content": "The -f switch displays the number of forks since boot.  This includes the fork, vfork,\nand clone system calls, and is equivalent to the total number of tasks created.   Each\nprocess  is represented by one or more tasks, depending on thread usage.  This display\ndoes not repeat.\n",
                    "flag": "-f",
                    "long": "--forks"
                },
                {
                    "name": "-m --slabs",
                    "content": "Displays slabinfo.\n",
                    "flag": "-m",
                    "long": "--slabs"
                },
                {
                    "name": "-n --one-header",
                    "content": "Display the header only once rather than periodically.\n",
                    "flag": "-n",
                    "long": "--one-header"
                },
                {
                    "name": "-s --stats",
                    "content": "Displays a table of various event counters and memory statistics.  This  display  does\nnot repeat.\n",
                    "flag": "-s",
                    "long": "--stats"
                },
                {
                    "name": "-d --disk",
                    "content": "Report disk statistics (2.5.70 or above required).\n",
                    "flag": "-d",
                    "long": "--disk"
                },
                {
                    "name": "-D --disk-sum",
                    "content": "Report some summary statistics about disk activity.\n",
                    "flag": "-D",
                    "long": "--disk-sum"
                },
                {
                    "name": "-p --partition",
                    "content": "Detailed statistics about partition (2.5.70 or above required).\n",
                    "flag": "-p",
                    "long": "--partition"
                },
                {
                    "name": "-S --unit",
                    "content": "Switches  outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes.  Note\nthis does not change the block (bi/bo) fields, which are always measured in blocks.\n",
                    "flag": "-S",
                    "long": "--unit"
                },
                {
                    "name": "-t --timestamp",
                    "content": "Append timestamp to each line\n",
                    "flag": "-t",
                    "long": "--timestamp"
                },
                {
                    "name": "-w --wide",
                    "content": "Wide output mode (useful for systems with higher amount of memory, where  the  default\noutput mode suffers from unwanted column breakage).  The output is wider than 80 char‐\nacters per line.\n",
                    "flag": "-w",
                    "long": "--wide"
                },
                {
                    "name": "-V --version",
                    "content": "Display version information and exit.\n",
                    "flag": "-V",
                    "long": "--version"
                },
                {
                    "name": "-h --help",
                    "content": "Display help and exit.\n",
                    "flag": "-h",
                    "long": "--help"
                }
            ]
        },
        "FIELD DESCRIPTION FOR VM MODE": {
            "content": "",
            "subsections": [
                {
                    "name": "Procs",
                    "content": "r: The number of runnable processes (running or waiting for run time).\nb: The number of processes blocked waiting for I/O to complete.\n"
                },
                {
                    "name": "Memory",
                    "content": "These are affected by the --unit option.\nswpd: the amount of swap memory used.\nfree: the amount of idle memory.\nbuff: the amount of memory used as buffers.\ncache: the amount of memory used as cache.\ninact: the amount of inactive memory.  (-a option)\nactive: the amount of active memory.  (-a option)\n"
                },
                {
                    "name": "Swap",
                    "content": "These are affected by the --unit option.\nsi: Amount of memory swapped in from disk (/s).\nso: Amount of memory swapped to disk (/s).\n\nIO\nbi: Blocks received from a block device (blocks/s).\nbo: Blocks sent to a block device (blocks/s).\n"
                },
                {
                    "name": "System",
                    "content": "in: The number of interrupts per second, including the clock.\ncs: The number of context switches per second.\n\nCPU\nThese are percentages of total CPU time.\nus: Time spent running non-kernel code.  (user time, including nice time)\nsy: Time spent running kernel code.  (system time)\nid: Time spent idle.  Prior to Linux 2.5.41, this includes IO-wait time.\nwa: Time spent waiting for IO.  Prior to Linux 2.5.41, included in idle.\nst: Time stolen from a virtual machine.  Prior to Linux 2.6.11, unknown.\n"
                }
            ]
        },
        "FIELD DESCRIPTION FOR DISK MODE": {
            "content": "",
            "subsections": [
                {
                    "name": "Reads",
                    "content": "total: Total reads completed successfully\nmerged: grouped reads (resulting in one I/O)\nsectors: Sectors read successfully\nms: milliseconds spent reading\n"
                },
                {
                    "name": "Writes",
                    "content": "total: Total writes completed successfully\nmerged: grouped writes (resulting in one I/O)\nsectors: Sectors written successfully\nms: milliseconds spent writing\n\nIO\ncur: I/O in progress\ns: seconds spent for I/O\n"
                }
            ]
        },
        "FIELD DESCRIPTION FOR DISK PARTITION MODE": {
            "content": "reads: Total number of reads issued to this partition\nread sectors: Total read sectors for partition\nwrites : Total number of writes issued to this partition\nrequested writes: Total number of write requests made for partition\n",
            "subsections": []
        },
        "FIELD DESCRIPTION FOR SLAB MODE": {
            "content": "cache: Cache name\nnum: Number of currently active objects\ntotal: Total number of available objects\nsize: Size of each object\npages: Number of pages with at least one active object\n",
            "subsections": []
        },
        "NOTES": {
            "content": "vmstat does not require special permissions.\n\nThese reports are intended to help identify system bottlenecks.  Linux vmstat does not  count\nitself as a running process.\n\nAll  linux blocks are currently 1024 bytes.  Old kernels may report blocks as 512 bytes, 2048\nbytes, or 4096 bytes.\n\nSince procps 3.1.9, vmstat lets you choose units (k, K, m, M).  Default is K (1024 bytes)  in\nthe default mode.\n\nvmstat uses slabinfo 1.1\n",
            "subsections": []
        },
        "FILES": {
            "content": "/proc/meminfo\n/proc/stat\n/proc/*/stat\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "free(1), iostat(1), mpstat(1), ps(1), sar(1), top(1)\n",
            "subsections": []
        },
        "BUGS": {
            "content": "Does not tabulate the block io per device or count the number of system calls.\n",
            "subsections": []
        },
        "AUTHORS": {
            "content": "Written by Henry Ware ⟨al172@yfn.ysu.edu⟩.\nFabian Frédérick ⟨ffrederick@users.sourceforge.net⟩ (diskstat, slab, partitions...)\n",
            "subsections": []
        },
        "REPORTING BUGS": {
            "content": "Please send bug reports to ⟨procps@freelists.org⟩\n\n\n\nprocps-ng                                    2020-06-04                                    VMSTAT(8)",
            "subsections": []
        }
    },
    "summary": "vmstat - Report virtual memory statistics",
    "flags": [
        {
            "flag": "-a",
            "long": "--active",
            "arg": null,
            "description": "Display active and inactive memory, given a 2.5.41 kernel or better."
        },
        {
            "flag": "-f",
            "long": "--forks",
            "arg": null,
            "description": "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."
        },
        {
            "flag": "-m",
            "long": "--slabs",
            "arg": null,
            "description": "Displays slabinfo."
        },
        {
            "flag": "-n",
            "long": "--one-header",
            "arg": null,
            "description": "Display the header only once rather than periodically."
        },
        {
            "flag": "-s",
            "long": "--stats",
            "arg": null,
            "description": "Displays a table of various event counters and memory statistics. This display does not repeat."
        },
        {
            "flag": "-d",
            "long": "--disk",
            "arg": null,
            "description": "Report disk statistics (2.5.70 or above required)."
        },
        {
            "flag": "-D",
            "long": "--disk-sum",
            "arg": null,
            "description": "Report some summary statistics about disk activity."
        },
        {
            "flag": "-p",
            "long": "--partition",
            "arg": null,
            "description": "Detailed statistics about partition (2.5.70 or above required)."
        },
        {
            "flag": "-S",
            "long": "--unit",
            "arg": null,
            "description": "Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes. Note this does not change the block (bi/bo) fields, which are always measured in blocks."
        },
        {
            "flag": "-t",
            "long": "--timestamp",
            "arg": null,
            "description": "Append timestamp to each line"
        },
        {
            "flag": "-w",
            "long": "--wide",
            "arg": null,
            "description": "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 char‐ acters per line."
        },
        {
            "flag": "-V",
            "long": "--version",
            "arg": null,
            "description": "Display version information and exit."
        },
        {
            "flag": "-h",
            "long": "--help",
            "arg": null,
            "description": "Display help and exit."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "free",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/free/1/json"
        },
        {
            "name": "iostat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/iostat/1/json"
        },
        {
            "name": "mpstat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/mpstat/1/json"
        },
        {
            "name": "ps",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/ps/1/json"
        },
        {
            "name": "sar",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/sar/1/json"
        },
        {
            "name": "top",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/top/1/json"
        }
    ]
}