26 Dec 2014
作用：查看内存总量和系统使用内存情况
语法：
free [-b | -k | -m | -g | -h] [-o] [-s delay ] [-c count ] [-a] [-t] [-l] [-V]
参数：
-b/-k/-m/-g, 用不同单位显示输出内容-h, 人类友好视图-t, 增加一行total统计行PS: buffers/cache(free):空余的buffers、cache和空余的内存之和才是系统当前实际可用内存 buffers是即将要被写入磁盘的，cache是被从磁盘中读出来的
输出内容含义：
free -m
total used free shared buffers cached
Mem: 3726 508 3217 0 43 141
-/+ buffers/cache: 323 3402
Swap: 763 0 763
## 第1行，标题行
## 第2行
# total：物理内存容量，total=used+free 3726约=508+3217
# used：系统使用的内存，包含buffers和cached
# free：空闲内存
# shared：基本已经停用
# buffers：写入到硬盘的缓存
# cached：供系统读取的缓存
## 第3行
# 1、used-cached-buffers 508-43-141约=323，含义为除buffers和cached以外真正用掉的内存
# 2、free+cached+buffers 3217+43+141约=3402，含义为包含buffers和cached真正可用的内存
## 第4行
# swap，基本是不会使用到
作用：输出虚拟memory的统计
man page description vmstat - Report virtual memory statistics
语法：vmstat [参数 内容] [延迟时间 [次数] ]
vmstat [-a] [-n] [-t] [-S unit] [delay [ count]]vmstat [-s] [-n] [-S unit]vmstat [-m] [-n] [delay [ count]]vmstat [-d] [-n] [delay [ count]]vmstat [-p disk partition] [-n] [delay [ count]]vmstat [-f]vmstat [-V]参数：
-s 转为显示一个统计表，包含各种系统memory信息，此信息不会重复刷新输出内容含义：
用法示例：
# "-s"参数会将输出结果由默认的memory status转换成一个静态报表 vmstat -s 1030528 total memory 491288 used memory 239108 active memory 189752 inactive memory 539240 free memory 159048 buffer memory 258412 swap cache 1023992 total swap 0 used swap 1023992 free swap 2655 non-nice user cpu ticks 87 nice user cpu ticks 28642 system cpu ticks 85839705 idle cpu ticks 113674 IO-wait cpu ticks 1905 IRQ cpu ticks 36223 softirq cpu ticks 0 stolen cpu ticks 228627 pages paged in 956490 pages paged out 0 pages swapped in 0 pages swapped out 10512745 interrupts 6644499 CPU context switches 1419434147 boot time 13994 forks
作用：储存内存信息
用法举例：
# 用MB来展示结果 cat /proc/meminfo|sed -r 's/ +/ /g'|\ awk -v unit="MB" -F ' ' '{$2=$2/1024}{printf("%20s %-9d %s\n",$1,$2,unit)}' MemTotal: 981 MB MemFree: 844 MB Buffers: 29 MB Cached: 35 MB SwapCached: 0 MB Active: 33 MB Inactive: 41 MB Active(anon): 8 MB Inactive(anon): 0 MB Active(file): 24 MB Inactive(file): 41 MB Unevictable: 0 MB Mlocked: 0 MB SwapTotal: 999 MB SwapFree: 999 MB Dirty: 0 MB Writeback: 0 MB AnonPages: 8 MB Mapped: 6 MB Shmem: 0 MB Slab: 38 MB SReclaimable: 14 MB SUnreclaim: 23 MB KernelStack: 1 MB PageTables: 1 MB NFS_Unstable: 0 MB Bounce: 0 MB WritebackTmp: 0 MB CommitLimit: 1490 MB Committed_AS: 58 MB VmallocTotal: 33554431 MB VmallocUsed: 151 MB VmallocChunk: 33554273 MB HardwareCorrupted: 0 MB AnonHugePages: 0 MB HugePages_Total: 0 MB HugePages_Free: 0 MB HugePages_Rsvd: 0 MB HugePages_Surp: 0 MB Hugepagesize: 2 MB DirectMap4k: 6 MB DirectMap2M: 1018 MB DirectMap1G: 0 MB