From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932257AbaFCG1q (ORCPT ); Tue, 3 Jun 2014 02:27:46 -0400 Received: from cantor2.suse.de ([195.135.220.15]:60925 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932203AbaFCG1o (ORCPT ); Tue, 3 Jun 2014 02:27:44 -0400 Date: Tue, 3 Jun 2014 08:27:42 +0200 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Hugh Dickins , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org Subject: Re: [patch v2] mm, memcg: periodically schedule when emptying page list Message-ID: <20140603062742.GA1321@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 02-06-14 17:51:25, David Rientjes wrote: > From: Hugh Dickins > > mem_cgroup_force_empty_list() can iterate a large number of pages on an lru and > mem_cgroup_move_parent() doesn't return an errno unless certain criteria, none > of which indicate that the iteration may be taking too long, is met. > > We have encountered the following stack trace many times indicating > "need_resched set for > 51000020 ns (51 ticks) without schedule", for example: > > scheduler_tick() > > mem_cgroup_move_account+0x4d/0x1d5 > mem_cgroup_move_parent+0x8d/0x109 > mem_cgroup_reparent_charges+0x149/0x2ba > mem_cgroup_css_offline+0xeb/0x11b > cgroup_offline_fn+0x68/0x16b > process_one_work+0x129/0x350 > > If this iteration is taking too long, we still need to do cond_resched() even > when an individual page is not busy. > > [rientjes@google.com: changelog] > Signed-off-by: Hugh Dickins > Signed-off-by: David Rientjes Acked-by: Michal Hocko Thanks! > --- > v2: always reschedule if needed, "page" itself may not have a pc mismatch > or been unable to isolate. > > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4784,9 +4784,9 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg, > if (mem_cgroup_move_parent(page, pc, memcg)) { > /* found lock contention or "pc" is obsolete. */ > busy = page; > - cond_resched(); > } else > busy = NULL; > + cond_resched(); > } while (!list_empty(list)); > } > -- Michal Hocko SUSE Labs