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 D79048E0001 for ; Tue, 18 Dec 2018 04:23:56 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id y35so11951661edb.5 for ; Tue, 18 Dec 2018 01:23:56 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id g21si5237277edj.72.2018.12.18.01.23.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 01:23:55 -0800 (PST) Subject: Re: [PATCH 07/14] mm, compaction: Always finish scanning of a full pageblock References: <20181214230310.572-1-mgorman@techsingularity.net> <20181214230310.572-8-mgorman@techsingularity.net> From: Vlastimil Babka Message-ID: Date: Tue, 18 Dec 2018 10:23:54 +0100 MIME-Version: 1.0 In-Reply-To: <20181214230310.572-8-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 , Linus Torvalds , Michal Hocko , ying.huang@intel.com, kirill@shutemov.name, Andrew Morton , Linux List Kernel Mailing On 12/15/18 12:03 AM, Mel Gorman wrote: > When compaction is finishing, it uses a flag to ensure the pageblock is > complete. However, in general it makes sense to always complete migration > of a pageblock. Minimally, skip information is based on a pageblock and > partially scanned pageblocks may incur more scanning in the future. The > pageblock skip handling also becomes more strict later in the series and > the hint is more useful if a complete pageblock was always scanned. > > The impact here is potentially on latencies as more scanning is done > but it's not a consistent win or loss as the scanning is not always a > high percentage of the pageblock and sometimes it is offset by future > reductions in scanning. Hence, the results are not presented this time as > it's a mix of gains/losses without any clear pattern. However, completing > scanning of the pageblock is important for later patches. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka