如何查看Linux中交换内存的内容？

Question

我试图找出我的系统中到底是什么使用了交换内存。免费报告使用的交换内存超过 5GB，但所有进程仅使用 24MB 的交换内存。我怀疑交换可能被 tmpfs 文件系统使用，但我不知道如何检查它。

您能告诉我还应该检查什么来检查交换内存的内容吗？

    # free -m
                 total       used       free     shared    buffers     cached
    Mem:         48206      47688        518       8177         10      11789
    -/+ buffers/cache:      35888      12317
    Swap:        15999       5378      10621

• 来自 /proc/*/status 的 VmSwap

  # grep "VmSwap:" /proc/*/status | awk '{swapped+=$2} END {print swapped/1024" MB"}'
  23.8438 MB
  
  # grep "VmSwap:" /proc/*/status | grep -v " 0 kB"
  /proc/1/status:VmSwap:        52 kB
  /proc/27714/status:VmSwap:           956 kB
  /proc/27718/status:VmSwap:           948 kB
  /proc/27722/status:VmSwap:           820 kB
  /proc/27723/status:VmSwap:           804 kB
  /proc/27724/status:VmSwap:           812 kB
  /proc/27725/status:VmSwap:           804 kB
  /proc/29636/status:VmSwap:           760 kB
  /proc/29640/status:VmSwap:           960 kB
  /proc/29642/status:VmSwap:          1948 kB
  /proc/29643/status:VmSwap:           936 kB
  /proc/29647/status:VmSwap:          1624 kB
  /proc/29649/status:VmSwap:           872 kB
  /proc/3750/status:VmSwap:            116 kB
  /proc/3770/status:VmSwap:            228 kB
  /proc/3790/status:VmSwap:            260 kB
  /proc/3810/status:VmSwap:            444 kB
  /proc/3823/status:VmSwap:            164 kB
  /proc/4022/status:VmSwap:           2296 kB
  /proc/4037/status:VmSwap:            640 kB
  /proc/4049/status:VmSwap:            572 kB
  /proc/4058/status:VmSwap:            592 kB
  /proc/4068/status:VmSwap:            260 kB
  /proc/4081/status:VmSwap:            192 kB
  /proc/4095/status:VmSwap:             56 kB
  /proc/4110/status:VmSwap:             76 kB
  /proc/4112/status:VmSwap:             80 kB
  /proc/4114/status:VmSwap:             76 kB
  /proc/4116/status:VmSwap:             80 kB
  /proc/4118/status:VmSwap:             80 kB
  /proc/4120/status:VmSwap:             76 kB
  /proc/4127/status:VmSwap:           2068 kB
  /proc/4128/status:VmSwap:           2068 kB
  /proc/7655/status:VmSwap:            312 kB
  /proc/7661/status:VmSwap:            380 kB
  /proc/905/status:VmSwap:             840 kB
  

• 临时文件系统

  # mount | grep tmpfs
  tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
  

• /proc/内存信息

  # cat /proc/meminfo           
  MemTotal:       49363344 kB
  MemFree:          700676 kB
  Buffers:           11000 kB
  Cached:         11822364 kB
  SwapCached:       522436 kB
  Active:         37945008 kB
  Inactive:        4986964 kB
  Active(anon):   35707220 kB
  Inactive(anon):  3720092 kB
  Active(file):    2237788 kB
  Inactive(file):  1266872 kB
  Unevictable:           0 kB
  Mlocked:               0 kB
  SwapTotal:      16383992 kB
  SwapFree:       10875936 kB
  Dirty:            224072 kB
  Writeback:             0 kB
  AnonPages:      30580752 kB
  Mapped:         12218972 kB
  Shmem:           8328572 kB
  Slab:             270104 kB
  SReclaimable:     181768 kB
  SUnreclaim:        88336 kB
  KernelStack:        4256 kB
  PageTables:        91528 kB
  NFS_Unstable:          0 kB
  Bounce:                0 kB
  WritebackTmp:          0 kB
  CommitLimit:    41065664 kB
  Committed_AS:   49589524 kB
  VmallocTotal:   34359738367 kB
  VmallocUsed:     5203000 kB
  VmallocChunk:   34327589304 kB
  HardwareCorrupted:     0 kB
  AnonHugePages:   5289984 kB
  HugePages_Total:       0
  HugePages_Free:        0
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:       2048 kB
  DirectMap4k:    31952556 kB
  DirectMap2M:    17270784 kB
  DirectMap1G:     1048576 kB
  

编辑：

问题解决了，找到一条信息，1372500页共享内存被交换：

    # ipcs -mu

    ------ Shared Memory Status --------
    segments allocated 32
    pages allocated 2752532
    pages resident  1380020
    pages swapped   1372500
    Swap performance: 0 attempts     0 successes

    # getconf PAGESIZE
    4096
    # echo $((1372500*4096/1024/1024))
    5361

Answer 1

Linux 将不经常访问的内存移至交换区；当时是否有空闲内存并不总是重要的，请参阅askubuntu上类似问题的答案： https: //askubuntu.com/a/159358