vmstat

　　实时查看内存使用情况

vmstat 2(秒数)
vmstat 5 40

vmstat 可用来记录 processes, memory, paging, block IO, traps, 与cpu activity。

例如

$ vmstat 1 # 1 是更新速度，单位为秒
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 549368 13316 102388 91992 12 6 9 8 2 12 72 3 25 0
2 0 549368 13316 102388 91992 0 0 0 0 156 1516 98 2 0 0
2 0 549368 13312 102388 91992 0 0 0 0 125 534 99 1 0 0

....

第一列與第二列所代表是執行程式的資訊，接下來的是記憶體、swap、io、systm 與 cpu。

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, shown as zero.