From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754948AbdCIO7m (ORCPT <rfc822;w@1wt.eu>);
        Thu, 9 Mar 2017 09:59:42 -0500
Received: from mx2.suse.de ([195.135.220.15]:52983 "EHLO mx2.suse.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1754647AbdCIO7l (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 9 Mar 2017 09:59:41 -0500
Date: Thu, 9 Mar 2017 15:59:38 +0100
From: Michal Hocko <mhocko@kernel.org>
To: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, Johannes Weiner <hannes@cmpxchg.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, vmscan: do not loop on too_many_isolated for ever
Message-ID: <20170309145937.GK11592@dhcp22.suse.cz>
References: <20170307133057.26182-1-mhocko@kernel.org>
 <1488916356.6405.4.camel@redhat.com>
 <20170308092114.GB11028@dhcp22.suse.cz>
 <1488988497.8850.23.camel@redhat.com>
 <20170309091224.GC11592@dhcp22.suse.cz>
 <1489068985.1906.1.camel@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <1489068985.1906.1.camel@redhat.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu 09-03-17 09:16:25, Rik van Riel wrote:
> On Thu, 2017-03-09 at 10:12 +0100, Michal Hocko wrote:
> > On Wed 08-03-17 10:54:57, Rik van Riel wrote:
> 
> > > In fact, false OOM kills with that kind of workload is
> > > how we ended up getting the "too many isolated" logic
> > > in the first place.
> > Right, but the retry logic was considerably different than what we
> > have these days. should_reclaim_retry considers amount of reclaimable
> > memory. As I've said earlier if we see a report where the oom hits
> > prematurely with many NR_ISOLATED* we know how to fix that.
> 
> Would it be enough to simply reset no_progress_loops
> in this check inside should_reclaim_retry, if we know
> pageout IO is pending?
> 
>                         if (!did_some_progress) {
>                                 unsigned long write_pending;
> 
>                                 write_pending = zone_page_state_snapshot(zone,
>                                                         NR_ZONE_WRITE_PENDING);
> 
>                                 if (2 * write_pending > reclaimable) {
>                                         congestion_wait(BLK_RW_ASYNC, HZ/10);
>                                         return true;
>                                 }
>                         }

I am not really sure what problem we are trying to solve right now to be
honest. I would prefer to keep the logic simpler rather than over
engeneer something that is even not needed.

-- 
Michal Hocko
SUSE Labs