From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751860AbdECHHH (ORCPT ); Wed, 3 May 2017 03:07:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:33207 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751042AbdECHG7 (ORCPT ); Wed, 3 May 2017 03:06:59 -0400 Date: Wed, 3 May 2017 09:06:56 +0200 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Minchan Kim , Johannes Weiner , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free + file is low Message-ID: <20170503070656.GA8836@dhcp22.suse.cz> References: <20170418013659.GD21354@bbox> <20170419001405.GA13364@bbox> <20170420060904.GA3720@bbox> <20170502080246.GD14593@dhcp22.suse.cz> <20170503061528.GB1236@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170503061528.GB1236@dhcp22.suse.cz> 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 Wed 03-05-17 08:15:28, Michal Hocko wrote: > On Tue 02-05-17 13:41:23, David Rientjes wrote: > > On Tue, 2 May 2017, Michal Hocko wrote: [...] > > > I do agree that blindly > > > scanning anon pages when file pages are low is very suboptimal but this > > > adds yet another heuristic without _any_ numbers. Why cannot we simply > > > treat anon and file pages equally? Something like the following > > > > > > if (pgdatfile + pgdatanon + pgdatfree > 2*total_high_wmark) { > > > scan_balance = SCAN_FILE; > > > if (pgdatfile < pgdatanon) > > > scan_balance = SCAN_ANON; > > > goto out; > > > } > > > > > > > This would be substantially worse than the current code because it > > thrashes the anon lru when anon out numbers file pages rather than at the > > point we fall under the high watermarks for all eligible zones. If you > > tested your suggestion, you could see gigabytes of memory left untouched > > on the file lru. Anonymous memory is more probable to be part of the > > working set. > > This was supposed to be more an example of a direction I was thinking, > definitely not a final patch. I will think more to come up with a > more complete proposal. This is still untested but should be much closer to what I've had in mind. --- diff --git a/mm/vmscan.c b/mm/vmscan.c index 24efcc20af91..bcdad30f942d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2174,8 +2174,14 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, } if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) { - scan_balance = SCAN_ANON; - goto out; + unsigned long pgdatanon; + + pgdatanon = node_page_state(pgdat, NR_ACTIVE_ANON) + + node_page_state(pgdat, NR_INACTIVE_ANON); + if (pgdatanon + pgdatfree > total_high_wmark) { + scan_balance = SCAN_ANON; + goto out; + } } } -- Michal Hocko SUSE Labs