From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751306AbdISDi0 (ORCPT ); Mon, 18 Sep 2017 23:38:26 -0400 Received: from mail-qt0-f176.google.com ([209.85.216.176]:51085 "EHLO mail-qt0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbdISDiZ (ORCPT ); Mon, 18 Sep 2017 23:38:25 -0400 X-Google-Smtp-Source: AOwi7QBcBXepx65eUyy1rfHjPEUvzAyaTpOGIeJh8+DcZbCUYEl/m6acEMnVy9CnPRNLAIhT4Vf7PA== Date: Mon, 18 Sep 2017 20:38:22 -0700 From: Tejun Heo To: Michal Hocko Cc: Tetsuo Handa , Andrew Morton , Mel Gorman , linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm, memory_hotplug: do not back off draining pcp free pages from kworker context Message-ID: <20170919033821.GR378890@devbig577.frc2.facebook.com> References: <20170828093341.26341-1-mhocko@kernel.org> <20170828153359.f9b252f99647eebd339a3a89@linux-foundation.org> <6e138348-aa28-8660-d902-96efafe1dcb2@I-love.SAKURA.ne.jp> <20170829112823.GA12413@dhcp22.suse.cz> <20170831053342.fo7x4hnhicxikme4@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170831053342.fo7x4hnhicxikme4@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Sorry about the delay. On Thu, Aug 31, 2017 at 07:33:42AM +0200, Michal Hocko wrote: > > > Michal, are you sure that this patch does not cause deadlock? > > > > > > As shown in "[PATCH] mm: Use WQ_HIGHPRI for mm_percpu_wq." thread, currently work > > > items on mm_percpu_wq seem to be blocked by other work items not on mm_percpu_wq. IIUC that wasn't a deadlock but more a legitimate starvation from too many tasks trying to reclaim directly. > > But we have a rescuer so we should make a forward progress eventually. > > Or am I missing something. Tejun, could you have a look please? > > ping... I would really appreaciate if you could double check my thinking > Tejun. This is a tricky area and I would like to prevent further subtle > issues here. So, this shouldn't be an issue. This may get affected by direct reclaim frenzy but it's only a small piece of the whole symptom and we gotta fix that at the source. Thanks. -- tejun