From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f54.google.com (mail-wm0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id 49F056B0254 for ; Wed, 25 Nov 2015 08:47:55 -0500 (EST) Received: by wmww144 with SMTP id w144so70032832wmw.0 for ; Wed, 25 Nov 2015 05:47:54 -0800 (PST) Received: from mail-wm0-f50.google.com (mail-wm0-f50.google.com. [74.125.82.50]) by mx.google.com with ESMTPS id v4si5920268wma.96.2015.11.25.05.47.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 25 Nov 2015 05:47:54 -0800 (PST) Received: by wmww144 with SMTP id w144so70032171wmw.0 for ; Wed, 25 Nov 2015 05:47:53 -0800 (PST) Date: Wed, 25 Nov 2015 14:47:52 +0100 From: Michal Hocko Subject: Re: [PATCH] mm/vmstat: retrieve more accurate vmstat value Message-ID: <20151125134747.GH27283@dhcp22.suse.cz> References: <1448346123-2699-1-git-send-email-iamjoonsoo.kim@lge.com> <20151125120021.GA27342@dhcp22.suse.cz> <5655BB0A.90000@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5655BB0A.90000@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Joonsoo Kim , Andrew Morton , linux-kernel@vger.kernel.org, Christoph Lameter , linux-mm@kvack.org, Joonsoo Kim On Wed 25-11-15 14:43:38, Vlastimil Babka wrote: > On 11/25/2015 01:00 PM, Michal Hocko wrote: > > On Tue 24-11-15 15:22:03, Joonsoo Kim wrote: > >> When I tested compaction in low memory condition, I found that > >> my benchmark is stuck in congestion_wait() at shrink_inactive_list(). > >> This stuck last for 1 sec and after then it can escape. More investigation > >> shows that it is due to stale vmstat value. vmstat is updated every 1 sec > >> so it is stuck for 1 sec. > > > > Wouldn't it be sufficient to use zone_page_state_snapshot in > > too_many_isolated? > > That sounds better than the ad-hoc half-solution, yeah. > I don't know how performance sensitive the callers are, but maybe it could do a > non-snapshot check first, and only repeat with _snapshot when it's about to wait > (the result is true), just to make sure? I am not sure this is worth bothering. We are in the reclaim which is not a hot path. -- 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