From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753360AbbAUOjb (ORCPT ); Wed, 21 Jan 2015 09:39:31 -0500 Received: from cantor2.suse.de ([195.135.220.15]:54763 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752100AbbAUOjX (ORCPT ); Wed, 21 Jan 2015 09:39:23 -0500 Date: Wed, 21 Jan 2015 15:39:20 +0100 From: Michal Hocko To: Vinayak Menon Cc: Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hannes@cmpxchg.org, vdavydov@parallels.com, mgorman@suse.de, minchan@kernel.org Subject: Re: [PATCH v2] mm: vmscan: fix the page state calculation in too_many_isolated Message-ID: <20150121143920.GD23700@dhcp22.suse.cz> References: <1421235419-30736-1-git-send-email-vinmenon@codeaurora.org> <20150114165036.GI4706@dhcp22.suse.cz> <54B7F7C4.2070105@codeaurora.org> <20150116154922.GB4650@dhcp22.suse.cz> <54BA7D3A.40100@codeaurora.org> <54BC879C.90505@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54BC879C.90505@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 19-01-15 09:57:08, Vinayak Menon wrote: > On 01/18/2015 01:18 AM, Christoph Lameter wrote: > >On Sat, 17 Jan 2015, Vinayak Menon wrote: > > > >>which had not updated the vmstat_diff. This CPU was in idle for around 30 > >>secs. When I looked at the tvec base for this CPU, the timer associated with > >>vmstat_update had its expiry time less than current jiffies. This timer had > >>its deferrable flag set, and was tied to the next non-deferrable timer in the > > > >We can remove the deferrrable flag now since the vmstat threads are only > >activated as necessary with the recent changes. Looks like this could fix > >your issue? > > > > Yes, this should fix my issue. Does it? Because I would prefer not getting into un-synced state much more than playing around one specific place which shows the problems right now. > But I think we may need the fix in too_many_isolated, since there can still > be a delay of few seconds (HZ by default and even more because of reasons > pointed out by Michal) which will result in reclaimers unnecessarily > entering congestion_wait. No ? I think we can solve this as well. We can stick vmstat_shepherd into a kernel thread with a loop with the configured timeout and then create a mask of CPUs which need the update and run vmstat_update from IPI context (smp_call_function_many). We would have to drop cond_resched from refresh_cpu_vm_stats of course. The nr_zones x NR_VM_ZONE_STAT_ITEMS in the IPI context shouldn't be excessive but I haven't measured that so I might be easily wrong. Anyway, that should work more reliably than the current scheme and should help to reduce pointless wakeups which the original patchset was addressing. Or am I missing something? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f170.google.com (mail-lb0-f170.google.com [209.85.217.170]) by kanga.kvack.org (Postfix) with ESMTP id 44C916B0032 for ; Wed, 21 Jan 2015 09:39:24 -0500 (EST) Received: by mail-lb0-f170.google.com with SMTP id w7so832677lbi.1 for ; Wed, 21 Jan 2015 06:39:23 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id v3si19509007lae.26.2015.01.21.06.39.22 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 21 Jan 2015 06:39:22 -0800 (PST) Date: Wed, 21 Jan 2015 15:39:20 +0100 From: Michal Hocko Subject: Re: [PATCH v2] mm: vmscan: fix the page state calculation in too_many_isolated Message-ID: <20150121143920.GD23700@dhcp22.suse.cz> References: <1421235419-30736-1-git-send-email-vinmenon@codeaurora.org> <20150114165036.GI4706@dhcp22.suse.cz> <54B7F7C4.2070105@codeaurora.org> <20150116154922.GB4650@dhcp22.suse.cz> <54BA7D3A.40100@codeaurora.org> <54BC879C.90505@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54BC879C.90505@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: Vinayak Menon Cc: Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hannes@cmpxchg.org, vdavydov@parallels.com, mgorman@suse.de, minchan@kernel.org On Mon 19-01-15 09:57:08, Vinayak Menon wrote: > On 01/18/2015 01:18 AM, Christoph Lameter wrote: > >On Sat, 17 Jan 2015, Vinayak Menon wrote: > > > >>which had not updated the vmstat_diff. This CPU was in idle for around 30 > >>secs. When I looked at the tvec base for this CPU, the timer associated with > >>vmstat_update had its expiry time less than current jiffies. This timer had > >>its deferrable flag set, and was tied to the next non-deferrable timer in the > > > >We can remove the deferrrable flag now since the vmstat threads are only > >activated as necessary with the recent changes. Looks like this could fix > >your issue? > > > > Yes, this should fix my issue. Does it? Because I would prefer not getting into un-synced state much more than playing around one specific place which shows the problems right now. > But I think we may need the fix in too_many_isolated, since there can still > be a delay of few seconds (HZ by default and even more because of reasons > pointed out by Michal) which will result in reclaimers unnecessarily > entering congestion_wait. No ? I think we can solve this as well. We can stick vmstat_shepherd into a kernel thread with a loop with the configured timeout and then create a mask of CPUs which need the update and run vmstat_update from IPI context (smp_call_function_many). We would have to drop cond_resched from refresh_cpu_vm_stats of course. The nr_zones x NR_VM_ZONE_STAT_ITEMS in the IPI context shouldn't be excessive but I haven't measured that so I might be easily wrong. Anyway, that should work more reliably than the current scheme and should help to reduce pointless wakeups which the original patchset was addressing. Or am I missing something? -- Michal Hocko SUSE Labs -- 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