On Thu, Jul 14, 2016 at 10:13 AM, Oleg Nesterov <o...@redhat.com> wrote: > On 07/14, John Stultz wrote: >> >> So I am seeing synchronize_sched called, and its taking the >> !rcu_gp_is_expedited path when I see the particularly bad latencies. >> >> I wonder if I just mucked up applying the patch? > > Probably yes...
Hm. So I applied peterz patch to 4.7-rc7 and then diffed it to what I had and it was just whitespace changes. I've synched them up now, so I suspect my application isn't the issue now. Just to be clear, I'm not supposed to be applying this on-top of Paul's change, right? > Just in case, could you try the patch below? Of course, without other > optimizations from Peter, this change makes cgroup_threadgroup_rwsem > much worse than a plain rw_semaphore. > > Oleg. > > --- x/kernel/cgroup.c > +++ x/kernel/cgroup.c > @@ -5605,6 +5605,8 @@ int __init cgroup_init(void) > BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files)); > BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files)); > > + rcu_sync_enter(&cgroup_threadgroup_rwsem.rss); > + So adding this does make a huge difference ontop of Peter's patch. I'm seeing sub 200us values for everything. The biggest spike in my basic testing has been 138us. I'm also not seeing synchronize_sched being called nearly as often, and it doesn't seem to be being called in cgroup_procs_write path. thanks -john
