mem 分析

可以看出cache 适用了3GB； 

Cached (3.4 GB)
这就是 free 里显示的 buff/cache ≈ 3G 的主要部分。
它表示文件内容被缓存到内存里（page cache）。
举例：你 cat 或 less 一个大文件，下次再读的时候就会从这里命中，不用去磁盘。

[root@localhost ~]# cat /proc/meminfo | egrep "Cached|Buffers|Slab"
Buffers:            2108 kB
Cached:          3597940 kB  (~3.4 GB)
SwapCached:            0 kB
Slab:             178600 kB
[root@localhost ~]# cat /proc/meminfo 
MemTotal:       16266508 kB
MemFree:         8175208 kB
MemAvailable:   11578140 kB
Buffers:            2108 kB
Cached:          3597984 kB
SwapCached:            0 kB
Active:          4835132 kB
Inactive:        2519844 kB
Active(anon):    3755476 kB
Inactive(anon):     8732 kB
Active(file):    1079656 kB
Inactive(file):  2511112 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       4063228 kB
SwapFree:        4063228 kB
Dirty:               992 kB
Writeback:             0 kB
AnonPages:       3736572 kB
Mapped:           192196 kB
Shmem:              9324 kB
Slab:             178600 kB
SReclaimable:     132032 kB
SUnreclaim:        46568 kB
KernelStack:        6416 kB
PageTables:        22056 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    12196480 kB
Committed_AS:    4982352 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      173236 kB
VmallocChunk:   34359341052 kB
Percpu:             1472 kB
HardwareCorrupted:     0 kB
AnonHugePages:   3540992 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      180096 kB
DirectMap2M:     5062656 kB
DirectMap1G:    13631488 kB