at first ,thanks for your reply. but i also tested what you said, the problem is also. force_empty only call try_to_free_pages, not all the pages remove because mem_cgroup_reparent_charges moved #cd /sys/fs/cgroup/memory #mkdir a #echo 0 > a/cgroup.procs #sleep 1 #echo 0 > a/cgroup.procs #echo 1 > a/memory.force_empty #rmdir a #cat /proc/cgroups #subsys_name hierarchy num_cgroups enabled memory 2 2 1 the num_cgroups also not released 2017-08-10 15:10 GMT+08:00 Michal Hocko <mhocko@xxxxxxxxxx>: > On Wed 09-08-17 15:06:34, wang Yu wrote: >> Hello Johannes ,Michal,and Tejun: >> >> i using memcg v1, but some reason i want to context to memcg v2, >> but i can't, here is my step: >> #cat /proc/cgroups >> #subsys_name hierarchy num_cgroups enabled >> memory 5 1 1 >> #cd /sys/fs/cgroup/memory >> #mkdir a >> #echo 0 > a/cgroup.procs >> #sleep 1 >> #echo 0 > cgroup.procs > > This doesn't do what you think. It will try to add a non-existant pid 0 > to the root cgroup. You need to remove cgroup a. Moreover it is possible > that the `sleep' command will fault some page cache and that will stay > in memcg `a' until there is a memory pressure. cgroup v1 had > force_empty knob which you can use to drain the cgroup before removal. > Then you should be able to umount the v1 cgroup and mount v2. > -- > Michal Hocko > SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
