[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20160714171311.GB13434@redhat.com>
Date: Thu, 14 Jul 2016 19:13:12 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: John Stultz <john.stultz@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
lkml <linux-kernel@...r.kernel.org>,
Dmitry Shmidt <dimitrysh@...gle.com>,
Rom Lemarchand <romlem@...gle.com>,
Colin Cross <ccross@...gle.com>, Todd Kjos <tkjos@...gle.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: Severe performance regression w/ 4.4+ on Android due to cgroup
locking changes
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...
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);
+
get_user_ns(init_cgroup_ns.user_ns);
mutex_lock(&cgroup_mutex);
Powered by blists - more mailing lists