From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752547AbbJWIgR (ORCPT ); Fri, 23 Oct 2015 04:36:17 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:35563 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbbJWIgP (ORCPT ); Fri, 23 Oct 2015 04:36:15 -0400 Date: Fri, 23 Oct 2015 10:36:12 +0200 From: Michal Hocko To: Tetsuo Handa Cc: htejun@gmail.com, cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, rientjes@google.com, oleg@redhat.com, kwalker@redhat.com, akpm@linux-foundation.org, hannes@cmpxchg.org, vdavydov@parallels.com, skozina@redhat.com, mgorman@suse.de, riel@redhat.com Subject: Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()checks Message-ID: <20151023083612.GC2410@dhcp22.suse.cz> References: <20151022151528.GG30579@mtj.duckdns.org> <20151022153559.GF26854@dhcp22.suse.cz> <20151022153703.GA3899@mtj.duckdns.org> <20151022154922.GG26854@dhcp22.suse.cz> <20151022184226.GA19289@mtj.duckdns.org> <201510230642.HDF57807.QJtSOVFFOMLHOF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201510230642.HDF57807.QJtSOVFFOMLHOF@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 23-10-15 06:42:43, Tetsuo Handa wrote: > Tejun Heo wrote: > > On Thu, Oct 22, 2015 at 05:49:22PM +0200, Michal Hocko wrote: > > > I am confused. What makes rescuer to not run? Nothing seems to be > > > hogging CPUs, we are just out of workers which are loopin in the > > > allocator but that is preemptible context. > > > > It's concurrency management. Workqueue thinks that the pool is making > > positive forward progress and doesn't schedule anything else for > > execution while that work item is burning cpu cycles. > > Then, isn't below change easier to backport which will also alleviate > needlessly burning CPU cycles? This is quite obscure. If the vmstat_update fix needs workqueue tweaks as well then I would vote for your original patch which is clear, straightforward and easy to backport. If WQ_MEM_RECLAIM can really guarantee one worker as described in the documentation then I agree that fixing vmstat is a better fix. But that doesn't seem to be the case currently. > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3385,6 +3385,7 @@ retry: > ((gfp_mask & __GFP_REPEAT) && pages_reclaimed < (1 << order))) { > /* Wait for some write requests to complete then retry */ > wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50); > + schedule_timeout_uninterruptible(1); > goto retry; > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michal Hocko SUSE Labs