The percpu memory used by memcg cannot be cleared

[liujing<liujing@cmss.chinamobile.com>]

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\r\r\r\r\r\rhello，linux boss\r\r\r\r\r        I found a problem in the process of using linux memcg，When I turned swap off, the memcg memory I created with the following script could not be deleted with echo 0 > memory.force_empty, as explained below。\r\r\r\r\r----------------------------------------------------------------------------------------------------------\r\rstep1：swapoff -a\r\r\r\r\r\r\r\rstep2：use this script to create memcg\r\r\r\r\r\r\r#!/bin/bash\r\rmkdir -p /tmp/test\r\rfor i in 'seq 2000'\r\rdo\r\r        sudo mkdir -p /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}\r\r        sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}/tasks\r\r        sudo echo 'data' > /tmp/test/test$ {i}\r\r        sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/tasks\r\r        sudo rmdir /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}\r\rdone\r\r\r\r\r\r\r\rstep3：view /proc/cgroup and /proc/meminfo  files\r\r\r\r\r\r\r[root@localhost ~]# cat /proc/cgroups\r\r#subsys_name    hierarchy       num_cgroups     enabled\r\rcpuset                    10                   1                         1\r\rcpu                          4                     1                        1\r\rcpuacct                    4                     1                       1\r\rblkio                        13                   1                        1\r\rmemory                  14                 2009                   1\r\rdevices                      6                   94                       1\r\r\r\r\r\r\r[root@localhost ~]# cat /proc/meminfo | grep Percpu\r\rPercpu:           600576 kB\r\r\r\r\r\r\r\rstep4：when I use "echo 0 > /sys/fs/cgroup/memory/user.slice/user-0.slice/memory.force_empty", I find the num_cgroups of memory and percpu  have no changed\r\r\r\r\r\r\r[root@localhost ~]# echo 0 > /sys/fs/cgroup/memory/user.slice/user-0.slice/memory.force_empty\r\r[root@localhost ~]# cat /proc/cgroups\r\r#subsys_name    hierarchy       num_cgroups     enabled\r\rcpuset                    10      1       1\r\rcpu                          4       1       1\r\rcpuacct                   4       1       1\r\rblkio                       13      1       1\r\rmemory                  14      2039    1\r\rdevices                    6       87      1\r\r\r\r\r\r\r[root@localhost ~]# cat /proc/meminfo | grep Percpu\r\rPercpu:           600576 kB\r\r\r\r\r\r\r\rstep 5: when I use swapon -a to open swap, then echo 0 > /sys/fs/cgroup/memory/user.slice/user-0.slice/memory.force_empty again\r\r\r\r\r\r\r[root@localhost ~]# swapon -a\r\r[root@localhost ~]# echo 0 > /sys/fs/cgroup/memory/user.slice/user-0.slice/memory.force_empty\r\r\r\r\r\r\r\rstep 6: view /proc/cgroup and /proc/meminfo  files ,I found the the num_cgroups of memory and percpu  have been reduced. \r\r\r\r[root@localhost ~]# cat /proc/cgroups\r\r#subsys_name    hierarchy       num_cgroups     enabled\r\rcpuset                    10                         1                 1\r\rcpu                         4                          1                 1\r\rcpuacct                  4                          1                  1\r\rblkio                     13                         1                  1\r\rmemory                14                     185                 1\r\rdevices                    6                      87                 1\r\rfreezer                   9                          1                 1\r\r\r\r\r\r\r[root@localhost ~]# cat /proc/meminfo | grep Percpu\r\rPercpu:           120832 kB\r\r--------------------------------------------------------------------------------------------------------\r\r\r\r\r\r\r\rTherefore, I want to know why swap affects memcg memory reclamation,  echo 0 > memory.force_empty this interface should force the memory used by the cgroup to be reclaimed. \r\rI want to know why ,I look forward to hearing back from the community.\r\rThanks.\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r-----------------------------------------\r\r刘婧   计算产品部\r\r\r\r手机：18896725597\r\r邮箱：liujing@cmss.chinamobile.com\r\r中移（苏州）软件技术有限公司\r\r\r

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