From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754466AbbJUOzK (ORCPT ); Wed, 21 Oct 2015 10:55:10 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:33318 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbbJUOzH (ORCPT ); Wed, 21 Oct 2015 10:55:07 -0400 Date: Wed, 21 Oct 2015 16:55:05 +0200 From: Michal Hocko To: Christoph Lameter Cc: Tetsuo Handa , 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: <20151021145505.GE8805@dhcp22.suse.cz> References: <201510212126.JIF90648.HOOFJVFQLMStOF@I-love.SAKURA.ne.jp> <20151021143337.GD8805@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed 21-10-15 09:49:07, Christoph Lameter wrote: > On Wed, 21 Oct 2015, Michal Hocko wrote: > > > Because all the WQ workers are stuck somewhere, maybe in the memory > > allocation which cannot make any progress and the vmstat update work is > > queued behind them. > > > > At least this is my current understanding. > > Eww. Maybe need a queue that does not do such evil things as memory > allocation? I am not sure how to achieve that. Requiring non-sleeping worker would work out but do we have enough users to add such an API? I would rather see vmstat using dedicated kernel thread(s) for this this purpose. We have discussed that in the past but it hasn't led anywhere. Anyway the workaround for this issue seems to be pretty trivial and shouldn't affect users out of direct reclaim much so it sounds good enough to me. Longterm we should really get rid of scan_reclaimable from the direct reclaim altogether. -- Michal Hocko SUSE Labs