On Thu 31-12-20 18:39:55, Shakeel Butt wrote: > This patch adds swapcache stat for the cgroup v2. The swapcache > represents the memory that is accounted against both the memory and the > swap limit of the cgroup. The main motivation behind exposing the > swapcache stat is for enabling users to gracefully migrate from cgroup > v1's memsw counter to cgroup v2's memory and swap counters. > > Cgroup v1's memsw limit allows users to limit the memory+swap usage of a > workload but without control on the exact proportion of memory and swap. > Cgroup v2 provides separate limits for memory and swap which enables > more control on the exact usage of memory and swap individually for the > workload. > > With some little subtleties, the v1's memsw limit can be switched with > the sum of the v2's memory and swap limits. However the alternative for > memsw usage is not yet available in cgroup v2. Exposing per-cgroup > swapcache stat enables that alternative. Adding the memory usage and > swap usage and subtracting the swapcache will approximate the memsw > usage. This will help in the transparent migration of the workloads > depending on memsw usage and limit to v2' memory and swap counters. Could you expand a bit more on why memsw usage is important even in cgroup v2 land? How are you going to use the approximated value? I am not really objecting to adding this counter. We do export it for the global case and having a memcg view sounds useful for analysis. -- Michal Hocko SUSE Labs
