mount -t tmpfs -o size=64G test-oom /mnt
str='请替换为很长的字符串'
i=0
while true
do
((i++))
# 循环写
echo ${str} > /mnt/file${i}
echo ${i}
donefree -h对比:
# tmpfs刚挂载时
total used free shared buff/cache available
Mem: 3.8Gi 417Mi 3.4Gi 948Ki 168Mi 3.4Gi
# oom时
total used free shared buff/cache available
Mem: 3.8Gi 3.6Gi 71Mi 2.9Gi 3.2Gi 169Miqemu虚拟机中导出vmcore的方法请参考《内核调试方法》，虚拟机导出vmcore对比，用crash解析。
总内存3.8G，通过crash的命令kmem -i对比看出，发生oom时，大幅增加的内存有USED（增加约3.33G）和CACHED（增加约2.76G），小幅增加的有SLAB（增加约660M）。
mainline刚挂载tmpfs时:
free -h
total used free shared buff/cache available
Mem: 3.8Gi 691Mi 2.8Gi 956Ki 566Mi 3.1Gi
Swap: 0B 0B 0B
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 998421 3.8 GB ----
FREE 730449 2.8 GB 73% of TOTAL MEM
USED 267972 1 GB 26% of TOTAL MEM
SHARED 69276 270.6 MB 6% of TOTAL MEM
BUFFERS 783 3.1 MB 0% of TOTAL MEM
CACHED 139008 543 MB 13% of TOTAL MEM
SLAB 19389 75.7 MB 1% of TOTAL MEM
TOTAL HUGE 0 0 ----
HUGE FREE 0 0 0% of TOTAL HUGE
TOTAL SWAP 0 0 ----
SWAP USED 0 0 0% of TOTAL SWAP
SWAP FREE 0 0 0% of TOTAL SWAP
COMMIT LIMIT 499210 1.9 GB ----
COMMITTED 235188 918.7 MB 47% of TOTAL LIMITmainline快oom时:
free -h
total used free shared buff/cache available
Mem: 3.8Gi 3.4Gi 109Mi 2.3Gi 2.9Gi 440Mi
Swap: 0B 0B 0B
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 998421 3.8 GB ----
FREE 27664 108.1 MB 2% of TOTAL MEM
USED 970757 3.7 GB 97% of TOTAL MEM
SHARED 52113 203.6 MB 5% of TOTAL MEM
BUFFERS 285 1.1 MB 0% of TOTAL MEM
CACHED 702798 2.7 GB 70% of TOTAL MEM
SLAB 156596 611.7 MB 15% of TOTAL MEM
TOTAL HUGE 0 0 ----
HUGE FREE 0 0 0% of TOTAL HUGE
TOTAL SWAP 0 0 ----
SWAP USED 0 0 0% of TOTAL SWAP
SWAP FREE 0 0 0% of TOTAL SWAP
COMMIT LIMIT 499210 1.9 GB ----
COMMITTED 775490 3 GB 155% of TOTAL LIMIT4.19刚挂载tmpfs时:
free -h
total used free shared buff/cache available
Mem: 3.8Gi 724Mi 2.2Gi 8.0Mi 933Mi 2.9Gi
Swap: 0B 0B 0B
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 1006287 3.8 GB ----
FREE 582172 2.2 GB 57% of TOTAL MEM
USED 424115 1.6 GB 42% of TOTAL MEM
SHARED 27868 108.9 MB 2% of TOTAL MEM
BUFFERS 407 1.6 MB 0% of TOTAL MEM
CACHED 226288 883.9 MB 22% of TOTAL MEM
SLAB 23597 92.2 MB 2% of TOTAL MEM
TOTAL HUGE 0 0 ----
HUGE FREE 0 0 0% of TOTAL HUGE
TOTAL SWAP 0 0 ----
SWAP USED 0 0 0% of TOTAL SWAP
SWAP FREE 0 0 0% of TOTAL SWAP
COMMIT LIMIT 503143 1.9 GB ----
COMMITTED 251344 981.8 MB 49% of TOTAL LIMIT4.19快oom时:
free -h
total used free shared buff/cache available
Mem: 3.8Gi 1.1Gi 120Mi 1.9Gi 2.6Gi 561Mi
Swap: 0B 0B 0B
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 1006287 3.8 GB ----
FREE 30608 119.6 MB 3% of TOTAL MEM
USED 975679 3.7 GB 96% of TOTAL MEM
SHARED 25198 98.4 MB 2% of TOTAL MEM
BUFFERS 147 588 KB 0% of TOTAL MEM
CACHED 649817 2.5 GB 64% of TOTAL MEM
SLAB 150220 586.8 MB 14% of TOTAL MEM
TOTAL HUGE 0 0 ----
HUGE FREE 0 0 0% of TOTAL HUGE
TOTAL SWAP 0 0 ----
SWAP USED 0 0 0% of TOTAL SWAP
SWAP FREE 0 0 0% of TOTAL SWAP
COMMIT LIMIT 503143 1.9 GB ----
COMMITTED 755068 2.9 GB 150% of TOTAL LIMIT