1VMSTAT(8) System Administration VMSTAT(8)
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6 vmstat - Report virtual memory statistics
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9 vmstat [options] [delay [count]]
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12 vmstat reports information about processes, memory, paging, block IO,
13 traps, disks and cpu activity.
14 The first report produced gives averages since the last reboot. Addi‐
16 tional reports give information on a sampling period of length delay.
17 The process and memory reports are instantaneous in either case.
18
20 delay The delay between updates in seconds. If no delay is specified,
21 only one report is printed with the average values since boot.
22 count Number of updates. In absence of count, when delay is defined,
24 default is infinite.
25 -a, --active
27 Display active and inactive memory, given a 2.5.41 kernel or
28 better.
29 -f, --forks
31 The -f switch displays the number of forks since boot. This
32 includes the fork, vfork, and clone system calls, and is equiva‐
33 lent to the total number of tasks created. Each process is rep‐
34 resented by one or more tasks, depending on thread usage. This
35 display does not repeat.
36 -m, --slabs
38 Displays slabinfo.
39 -n, --one-header
41 Display the header only once rather than periodically.
42 -s, --stats
44 Displays a table of various event counters and memory statis‐
45 tics. This display does not repeat.
46 -d, --disk
48 Report disk statistics (2.5.70 or above required).
49 -D, --disk-sum
51 Report some summary statistics about disk activity.
52 -p, --partition device
54 Detailed statistics about partition (2.5.70 or above required).
55 -S, --unit character
57 Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or
58 1048576 (M) bytes. Note this does not change the block (bi/bo)
59 fields, which are always measured in blocks.
60 -t, --timestamp
62 Append timestamp to each line
63 -w, --wide
65 Wide output mode (useful for systems with higher amount of mem‐
66 ory, where the default output mode suffers from unwanted column
67 breakage). The output is wider than 80 characters per line.
68 -V, --version
70 Display version information and exit.
71 -h, --help
73 Display help and exit.
74
76 Procs
77 r: The number of runnable processes (running or waiting for run time).
78 b: The number of processes in uninterruptible sleep.
79 Memory
81 These are affected by the --unit option.
82 swpd: the amount of virtual memory used.
83 free: the amount of idle memory.
84 buff: the amount of memory used as buffers.
85 cache: the amount of memory used as cache.
86 inact: the amount of inactive memory. (-a option)
87 active: the amount of active memory. (-a option)
88 Swap
90 These are affected by the --unit option.
91 si: Amount of memory swapped in from disk (/s).
92 so: Amount of memory swapped to disk (/s).
93 IO
95 bi: Blocks received from a block device (blocks/s).
96 bo: Blocks sent to a block device (blocks/s).
97 System
99 in: The number of interrupts per second, including the clock.
100 cs: The number of context switches per second.
101 CPU
103 These are percentages of total CPU time.
104 us: Time spent running non-kernel code. (user time, including nice time)
105 sy: Time spent running kernel code. (system time)
106 id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
107 wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle.
108 st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.
109
111 Reads
112 total: Total reads completed successfully
113 merged: grouped reads (resulting in one I/O)
114 sectors: Sectors read successfully
115 ms: milliseconds spent reading
116 Writes
118 total: Total writes completed successfully
119 merged: grouped writes (resulting in one I/O)
120 sectors: Sectors written successfully
121 ms: milliseconds spent writing
122 IO
124 cur: I/O in progress
125 s: seconds spent for I/O
126
128 reads: Total number of reads issued to this partition
129 read sectors: Total read sectors for partition
130 writes : Total number of writes issued to this partition
131 requested writes: Total number of write requests made for partition
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134 cache: Cache name
135 num: Number of currently active objects
136 total: Total number of available objects
137 size: Size of each object
138 pages: Number of pages with at least one active object
139
141 vmstat does not require special permissions.
142 These reports are intended to help identify system bottlenecks. Linux
144 vmstat does not count itself as a running process.
145 All linux blocks are currently 1024 bytes. Old kernels may report
147 blocks as 512 bytes, 2048 bytes, or 4096 bytes.
148 Since procps 3.1.9, vmstat lets you choose units (k, K, m, M). Default
150 is K (1024 bytes) in the default mode.
151 vmstat uses slabinfo 1.1
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155 /proc/meminfo
156 /proc/stat
157 /proc/*/stat
158
160 free(1), iostat(1), mpstat(1), ps(1), sar(1), top(1)
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163 Does not tabulate the block io per device or count the number of system
164 calls.
165
167 Written by Henry Ware ⟨al172@yfn.ysu.edu⟩.
168 Fabian Frédérick ⟨ffrederick@users.sourceforge.net⟩ (diskstat, slab,
169 partitions...)
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172 Please send bug reports to ⟨procps@freelists.org⟩
173procps-ng September 2011 VMSTAT(8)