Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932476AbdCIOpC (ORCPT ); Thu, 9 Mar 2017 09:45:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:51477 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932381AbdCIOpB (ORCPT ); Thu, 9 Mar 2017 09:45:01 -0500 Date: Thu, 9 Mar 2017 15:44:48 +0100 From: Michal Hocko To: Mel Gorman Cc: Andrew Morton , Tetsuo Handa , Vlastimil Babka , linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm: move pcp and lru-pcp drainging into single wq Message-ID: <20170309144448.GJ11592@dhcp22.suse.cz> References: <20170307131751.24936-1-mhocko@kernel.org> <20170309142602.nhuawsps3mdxqxjv@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170309142602.nhuawsps3mdxqxjv@suse.de> 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 Content-Length: 2766 Lines: 72 On Thu 09-03-17 14:26:02, Mel Gorman wrote: > On Tue, Mar 07, 2017 at 02:17:51PM +0100, Michal Hocko wrote: > > From: Michal Hocko > > > > We currently have 2 specific WQ_RECLAIM workqueues in the mm code. > > vmstat_wq for updating pcp stats and lru_add_drain_wq dedicated to drain > > per cpu lru caches. This seems more than necessary because both can run > > on a single WQ. Both do not block on locks requiring a memory allocation > > nor perform any allocations themselves. We will save one rescuer thread > > this way. > > > > On the other hand drain_all_pages() queues work on the system wq which > > doesn't have rescuer and so this depend on memory allocation (when all > > workers are stuck allocating and new ones cannot be created). This is > > not critical as there should be somebody invoking the OOM killer (e.g. > > the forking worker) and get the situation unstuck and eventually > > performs the draining. Quite annoying though. This worker should be > > using WQ_RECLAIM as well. We can reuse the same one as for lru draining > > and vmstat. > > > > Changes since v1 > > - rename vmstat_wq to mm_percpu_wq - per Mel > > - make sure we are not trying to enqueue anything while the WQ hasn't > > been intialized yet. This shouldn't happen because the initialization > > is done from an init code but some init section might be triggering > > those paths indirectly so just warn and skip the draining in that case > > per Vlastimil > > - do not propagate error from setup_vmstat to keep the previous behavior > > per Mel > > > > Suggested-by: Tetsuo Handa > > Signed-off-by: Michal Hocko > > Acked-by: Mel Gorman Thanks! > > +struct workqueue_struct *mm_percpu_wq; > > + > > static int __init setup_vmstat(void) > > { > > -#ifdef CONFIG_SMP > > - int ret; > > + int ret __maybe_unused; > > > > + mm_percpu_wq = alloc_workqueue("vmstat", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0); > > + > > +#ifdef CONFIG_SMP > > ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead", > > NULL, vmstat_cpu_dead); > > if (ret < 0) > > Should the workqueue also have been renamed to mm_percpu_wq? Of course. Andrew, could you fold the following in --- diff --git a/mm/vmstat.c b/mm/vmstat.c index ff9c49c47f32..4bbc775f9d08 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1766,7 +1766,7 @@ static int __init setup_vmstat(void) { int ret __maybe_unused; - mm_percpu_wq = alloc_workqueue("vmstat", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0); + mm_percpu_wq = alloc_workqueue("mm_percpu_wq", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0); #ifdef CONFIG_SMP ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead", -- Michal Hocko SUSE Labs