Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753601AbbKBPBo (ORCPT ); Mon, 2 Nov 2015 10:01:44 -0500 Received: from mail-wi0-f176.google.com ([209.85.212.176]:36931 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633AbbKBPBk (ORCPT ); Mon, 2 Nov 2015 10:01:40 -0500 Date: Mon, 2 Nov 2015 16:01:37 +0100 From: Michal Hocko To: Tejun Heo Cc: Christoph Lameter , Tetsuo Handa , linux-mm@kvack.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, David Rientjes , 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: <20151102150137.GB3442@dhcp22.suse.cz> References: <20151022140944.GA30579@mtj.duckdns.org> <20151022142155.GB30579@mtj.duckdns.org> <20151022142429.GC30579@mtj.duckdns.org> <20151022143349.GD30579@mtj.duckdns.org> <20151022151414.GF30579@mtj.duckdns.org> <20151023042649.GB18907@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151023042649.GB18907@mtj.duckdns.org> 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 Content-Length: 1847 Lines: 38 On Fri 23-10-15 13:26:49, Tejun Heo wrote: > Hello, > > So, something like the following. Just compile tested but this is > essentially partial revert of 3270476a6c0c ("workqueue: reimplement > WQ_HIGHPRI using a separate worker_pool") - resurrecting the old > WQ_HIGHPRI implementation under WQ_IMMEDIATE, so we know this works. > If for some reason, it gets decided against simply adding one jiffy > sleep, please let me know. I'll verify the operation and post a > proper patch. That said, given that this prolly needs -stable > backport and vmstat is likely to be the only user (busy loops are > really rare in the kernel after all), I think the better approach > would be reinstating the short sleep. As already pointed out I really detest a short sleep and would prefer a way to tell WQ what we really need. vmstat is not the only user. OOM sysrq will need this special treatment as well. While the zone_reclaimable can be fixed in an easy patch (http://lkml.kernel.org/r/201510212126.JIF90648.HOOFJVFQLMStOF%40I-love.SAKURA.ne.jp) which is perfectly suited for the stable backport, OOM sysrq resp. any sysrq which runs from the WQ context should be as robust as possible and shouldn't rely on all the code running from WQ context to issue a sleep to get unstuck. So I definitely support something like this patch. I am still not sure whether other WQ_MEM_RECLAIM users needs this flag as well because I am not familiar with their implementation but at vmstat and sysrq should use it and should be safe to do so without risk of breaking anything AFAICS. Thanks! -- Michal Hocko SUSE Labs -- 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/