Li, On Fri, Feb 11, 2011 at 1:55 AM, Li Zefan <l...@cn.fujitsu.com> wrote: >>>> while there is already cgroup monitoring active. In that case and if we do >>>> not >>>> want to wait until there is at least one ctxsw on all CPUs, then we have to >>>> check if the other threads are not already running on the other CPUs.If so, >>>> we need to do a cgroup switch on those CPUs. Otherwise, we have nothing to >>>> do. Am I getting this right? >>> >>> Right, so if any of those tasks is currently running, that cpu will be >>> monitoring their old cgroup, hence we send an IPI to flip cgroups. >>> >> I have built a test case where this would trigger. I launched a >> multi-threaded >> app, and then I move the pid into a cgroup via: echo PID >> >/cgroup/tests/tasks. >> I don't see any perf_cgroup move beyond the PID passed. >> >> I looked at kernel/cgroup.c and I could not find a invocation of >> ss->attach() that >> would pass threadgroup = true. So I am confused here. >> >> I wonder how the cgroupfs 'echo PID >tasks' interface would make the >> distinction >> between PID and TID. It seems possible to move one thread of a multi-threaded >> process into a cgroup but not the others. >> > > You can do this: > > # echo PID > cgroup.procs > > When the patchset that implements the above feature is accepted. See: > > https://lkml.org/lkml/2011/2/7/418 > > The below commit that confused you is actually a part of the above patchset, > but it sneaked into the kernel accidentally: > > commit be367d09927023d081f9199665c8500f69f14d22 > Author: Ben Blum <bb...@google.com> > Date: Wed Sep 23 15:56:31 2009 -0700 > > cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time > Ok, that makes more sense now. I wil try with the above patchset applied to verify this work as expected.
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