From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id 375188E0002 for ; Tue, 15 Jan 2019 08:18:06 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id i55so1105882ede.14 for ; Tue, 15 Jan 2019 05:18:06 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id x52si9407032edx.285.2019.01.15.05.18.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Jan 2019 05:18:04 -0800 (PST) Subject: Re: [PATCH 10/25] mm, compaction: Ignore the fragmentation avoidance boost for isolation and compaction References: <20190104125011.16071-1-mgorman@techsingularity.net> <20190104125011.16071-11-mgorman@techsingularity.net> From: Vlastimil Babka Message-ID: <99d75a89-ef07-683a-761d-f800c53cc910@suse.cz> Date: Tue, 15 Jan 2019 14:18:03 +0100 MIME-Version: 1.0 In-Reply-To: <20190104125011.16071-11-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Linux-MM Cc: David Rientjes , Andrea Arcangeli , ying.huang@intel.com, kirill@shutemov.name, Andrew Morton , Linux List Kernel Mailing On 1/4/19 1:49 PM, Mel Gorman wrote: > When pageblocks get fragmented, watermarks are artifically boosted to > reclaim pages to avoid further fragmentation events. However, compaction > is often either fragmentation-neutral or moving movable pages away from > unmovable/reclaimable pages. As the true watermarks are preserved, allow > compaction to ignore the boost factor. > > The expected impact is very slight as the main benefit is that compaction > is slightly more likely to succeed when the system has been fragmented > very recently. On both 1-socket and 2-socket machines for THP-intensive > allocation during fragmentation the success rate was increased by less > than 1% which is marginal. However, detailed tracing indicated that > failure of migration due to a premature ENOMEM triggered by watermark > checks were eliminated. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 57ba9d1da519..05c9a81d54ed 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2958,7 +2958,7 @@ int __isolate_free_page(struct page *page, unsigned int order) > * watermark, because we already know our high-order page > * exists. > */ > - watermark = min_wmark_pages(zone) + (1UL << order); > + watermark = zone->_watermark[WMARK_MIN] + (1UL << order); > if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) > return 0; > >