vmstat
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[root@server70 ~]# vmstat -S M 1 10 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 11 770 1009 3119 0 0 28 22 53 51 4 1 94 1 0 3 0 11 727 1009 3120 0 0 52 2504 8387 2624 12 1 86 1 0 0 0 11 755 1009 3120 0 0 4 157 4619 1841 12 1 86 1 0 0 0 11 755 1009 3120 0 0 136 4 9405 1595 2 1 98 0 0 0 0 11 755 1009 3120 0 0 0 33 4564 875 0 0 99 0 0 1 0 11 761 1009 3120 0 0 60 0 3151 1157 2 1 97 0 0 0 0 11 798 1009 3120 0 0 12 984 2937 898 0 0 99 0 0 0 1 11 828 1009 3120 0 0 0 321 3108 1002 3 0 96 1 0 0 0 11 813 1009 3120 0 0 4 0 6065 1512 6 1 93 0 0 1 0 11 848 1009 3120 0 0 4 100 7311 1628 3 1 95 2 0 [root@server70 ~]# |
vmstat 1
* High values in “wa” column mean: IO problem
* High values in “si”, “so” mean: excessive swapping
Sustained high swap rates (si and so) are usually bad. The system will start spending all of its time swapping, and make no progress on any actual work. You will also see the number of runnable (r and b) processes increase. If the situation gets bad enough and free memory gets too low, the Out-of-memory (oom) logic will start killing random processes. At this point, either reducing the number of processes that normally run or adding additional RAM are about the only options.
vmstat – Report virtual memory statistics
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vmstat [-a] [-n] [delay [ count]] vmstat [-f] [-s] [-m] vmstat [-S unit] vmstat [-d] vmstat [-p disk partition] vmstat [-V] |
vmstat reports information about processes, memory, paging, block IO, traps, 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.
FIELD DESCRIPTION FOR VM MODE
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Procs r: The number of processes waiting for run time. b: The number of processes in uninterruptible sleep. Memory swpd: the amount of virtual 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 si: Amount of memory swapped in from disk (/s). so: Amount of memory swapped to disk (/s). IO bi: Blocks received from a block device (blocks/s). bo: Blocks sent to a block device (blocks/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. |
FIELD DESCRIPTION FOR DISK MODE
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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
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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
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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 totpages: Total number of allocated pages pslab: Number of pages per slab |
Related commands
* iostat
* sar
* mpstat
* ps
* top
* free
See Linux Commands