From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 2F5F68E0001 for ; Tue, 18 Dec 2018 08:52:00 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id b7so12626750eda.10 for ; Tue, 18 Dec 2018 05:52:00 -0800 (PST) Received: from outbound-smtp11.blacknight.com (outbound-smtp11.blacknight.com. [46.22.139.106]) by mx.google.com with ESMTPS id p10si2552321eds.243.2018.12.18.05.51.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 05:51:59 -0800 (PST) Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp11.blacknight.com (Postfix) with ESMTPS id 967611C2743 for ; Tue, 18 Dec 2018 13:51:58 +0000 (GMT) Date: Tue, 18 Dec 2018 13:51:56 +0000 From: Mel Gorman Subject: Re: [PATCH 09/14] mm, compaction: Ignore the fragmentation avoidance boost for isolation and compaction Message-ID: <20181218135156.GK29005@techsingularity.net> References: <20181214230310.572-1-mgorman@techsingularity.net> <20181214230310.572-10-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Linux-MM , David Rientjes , Andrea Arcangeli , Linus Torvalds , Michal Hocko , ying.huang@intel.com, kirill@shutemov.name, Andrew Morton , Linux List Kernel Mailing On Tue, Dec 18, 2018 at 01:36:42PM +0100, Vlastimil Babka wrote: > On 12/15/18 12:03 AM, Mel Gorman wrote: > > When pageblocks get fragmented, watermarks are artifically boosted to pages > > are reclaimed to avoid further fragmentation events. However, compaction > > is often either fragmentation-neutral or moving movable pages away from > > unmovable/reclaimable pages. As the actual watermarks are preserved, > > allow compaction to ignore the boost factor. > > Right, I should have realized that when reviewing the boost patch. I > think it would be useful to do the same change in > __compaction_suitable() as well. Compaction has its own "gap". > That gap is somewhat static though so I'm a bit more wary of it. However, the check in __isolate_free_page looks too agressive. We isolate in units of COMPACT_CLUSTER_MAX yet the watermark check there is based on the allocation request. That means for THP that we check if 512 pages can be allocated when only somewhere between 1 and 32 is needed for that compaction cycle to complete. Adjusting that might be more appropriate? -- Mel Gorman SUSE Labs