free命令查看内存信息

Posted 2020-12-24 standby

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free介绍

FREE(1)                       Linux User’s Manual                      FREE(1)

NAME
       free - Display amount of free and used memory in the system

SYNOPSIS
       free [-b | -k | -m] [-o] [-s delay ] [-t] [-l] [-V]

DESCRIPTION
       free  displays  the total amount of free and used physical and swap memory in the system, 
       as well as the buffers used by the kernel.  
       The shared memory column should be ignored; it is obsolete.

   Options
       The -b switch displays the amount of memory in bytes; the -k switch (set by default) displays  it
       in kilobytes; the -m switch displays it in megabytes.

       The -t switch displays a line containing the totals.

       The  -o  switch disables the display of a "buffer adjusted" line.  If the -o option is not speci-
       fied, free subtracts buffer memory from the used memory and adds it to the free memory  reported.

       The  -s  switch  activates  continuous  polling delay seconds apart. You may actually specify any
       floating point number for delay, usleep(3) is used for microsecond resolution delay times.

       The -l switch shows detailed low and high memory statistics.

       The -V switch displays version information.

FILES
       /proc/meminfo-- memory information

SEE ALSO
       ps(1), slabtop(1), vmstat(8), top(1)

AUTHORS
       Written by Brian Edmonds.

       Send bug reports to <[email protected]>

Cohesive Systems                 20 Mar 1993                           FREE(1)

free示例

[email protected][12:20:25]$ free && echo ‘‘ && cat /proc/meminfo
             total       used       free     shared    buffers     cached
Mem:      32880252    7804824   25075428       2836     397504    5559752
-/+ buffers/cache:    1847568   31032684
Swap:      2064380          0    2064380

MemTotal:       32880252 kB
MemFree:        25075428 kB
Buffers:          397504 kB
Cached:          5559752 kB
SwapCached:            0 kB
Active:          2778440 kB
Inactive:        4535288 kB
Active(anon):    1356660 kB
Inactive(anon):     2640 kB
Active(file):    1421780 kB
Inactive(file):  4532648 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       2064380 kB
SwapFree:        2064380 kB
Dirty:               160 kB
Writeback:             0 kB
AnonPages:       1356472 kB
Mapped:            32648 kB
Shmem:              2836 kB
Slab:             259528 kB
SReclaimable:     221788 kB
SUnreclaim:        37740 kB
KernelStack:        5776 kB
PageTables:        18332 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    18504504 kB
Committed_AS:    3346884 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       66544 kB
VmallocChunk:   34359658428 kB
HardwareCorrupted:     0 kB
AnonHugePages:    806912 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:        6012 kB
DirectMap2M:     2091008 kB
DirectMap1G:    31457280 kB
[email protected][12:20:30]$

字段解释

>>> # free 默认单位是KB
>>> 
>>> 32880252-7804824             # 总内存 - 已使用内存 == 剩余可用内存
25075428
>>> 
>>> 7804824-397504-5559752       # 已使用内存分为三部分：应用程序占用的内存 + buffers + cached
1847568                          # 所以当前服务器上应用程序一共占用了 1847568KB内存
>>> 
>>> 25075428+397504+5559752      # 全部可用内存 = 剩余可用内存 + buffers + cached
31032684                         # 所以当前服务器上可以实际使用的内存为 31032684KB
>>>