From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f177.google.com (mail-io0-f177.google.com [209.85.223.177]) by kanga.kvack.org (Postfix) with ESMTP id C2ECE82F64 for ; Fri, 6 Nov 2015 07:56:30 -0500 (EST) Received: by ioc74 with SMTP id 74so57230998ioc.2 for ; Fri, 06 Nov 2015 04:56:30 -0800 (PST) Received: from resqmta-ch2-12v.sys.comcast.net (resqmta-ch2-12v.sys.comcast.net. [2001:558:fe21:29:69:252:207:44]) by mx.google.com with ESMTPS id v10si590724igz.2.2015.11.06.04.56.30 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 06 Nov 2015 04:56:30 -0800 (PST) Date: Fri, 6 Nov 2015 06:56:28 -0600 (CST) From: Christoph Lameter Subject: Re: [patch 3/3] vmstat: Create our own workqueue In-Reply-To: <201511062028.DFE13506.MtVSOOFJLFOHQF@I-love.SAKURA.ne.jp> Message-ID: References: <20151029022447.GB27115@mtj.duckdns.org> <20151029030822.GD27115@mtj.duckdns.org> <201510311143.BIH87000.tOSVFHOFJMLFOQ@I-love.SAKURA.ne.jp> <201511062028.DFE13506.MtVSOOFJLFOHQF@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: htejun@gmail.com, akpm@linux-foundation.org, mhocko@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, hannes@cmpxchg.org, mgorman@suse.de On Fri, 6 Nov 2015, Tetsuo Handa wrote: > So, if you refer to the blocking of the execution of vmstat updates, > description for patch 3/3 sould be updated to something like below? Ok that is much better. > ---------- > Since __GFP_WAIT memory allocations do not call schedule() > when there is nothing to reclaim, and workqueue does not kick > remaining workqueue items unless in-flight workqueue item calls > schedule(), __GFP_WAIT memory allocation requests by workqueue > items can block vmstat_update work item forever. > > Since zone_reclaimable() decision depends on vmstat counters > to be up to dated, a silent lockup occurs because a workqueue > item doing a __GFP_WAIT memory allocation request continues > using outdated vmstat counters. > > In order to fix this problem, we need to allocate a dedicated > workqueue for vmstat. Note that this patch itself does not fix > lockup problem. Tejun will develop a patch which detects lockup > situation and kick remaining workqueue items. > ---------- > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org