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 994F48E0001 for ; Tue, 18 Dec 2018 03:38:27 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id c53so11894817edc.9 for ; Tue, 18 Dec 2018 00:38:27 -0800 (PST) Received: from outbound-smtp16.blacknight.com (outbound-smtp16.blacknight.com. [46.22.139.233]) by mx.google.com with ESMTPS id 89si2191361edr.235.2018.12.18.00.38.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 00:38:26 -0800 (PST) Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp16.blacknight.com (Postfix) with ESMTPS id C816C1C18EB for ; Tue, 18 Dec 2018 08:38:25 +0000 (GMT) Date: Tue, 18 Dec 2018 08:38:24 +0000 From: Mel Gorman Subject: Re: [PATCH 05/14] mm, compaction: Skip pageblocks with reserved pages Message-ID: <20181218083823.GI29005@techsingularity.net> References: <20181214230310.572-1-mgorman@techsingularity.net> <20181214230310.572-6-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 09:08:02AM +0100, Vlastimil Babka wrote: > On 12/15/18 12:03 AM, Mel Gorman wrote: > > Reserved pages are set at boot time, tend to be clustered and almost > > never become unreserved. When isolating pages for migrating, skip > > the entire pageblock is one PageReserved page is encountered on the > > grounds that it is highly probable the entire pageblock is reserved. > > Agreed, but maybe since it's highly probable and not certain, this > skipping should not be done on the highest compaction priority? > I don't think that's necessary at this time. For the most part, you are talking about one partial pageblock at best given how the early memory allocator works so it would only ever be useful for a high-order kernel allocation. Second, one of compactions primary problems is inefficient scanning where viable pageblocks are easily skipped over or only partially scanned which is something I'm still looking at. Lastly, maximum priority compaction is rarely hit in practice as far as I can tell. -- Mel Gorman SUSE Labs