From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24C43C43387 for ; Fri, 18 Jan 2019 09:18:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3D902086D for ; Fri, 18 Jan 2019 09:18:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726919AbfARJSA (ORCPT ); Fri, 18 Jan 2019 04:18:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:41108 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725924AbfARJR7 (ORCPT ); Fri, 18 Jan 2019 04:17:59 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id AA2BFAEF0; Fri, 18 Jan 2019 09:17:58 +0000 (UTC) Subject: Re: [PATCH 21/25] mm, compaction: Round-robin the order while searching the free lists for a target To: Mel Gorman , Linux-MM Cc: David Rientjes , Andrea Arcangeli , ying.huang@intel.com, kirill@shutemov.name, Andrew Morton , Linux List Kernel Mailing References: <20190104125011.16071-1-mgorman@techsingularity.net> <20190104125011.16071-22-mgorman@techsingularity.net> From: Vlastimil Babka Message-ID: <71ad4f46-ca81-9a70-0b98-d1a1c46df47a@suse.cz> Date: Fri, 18 Jan 2019 10:17:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190104125011.16071-22-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/4/19 1:50 PM, Mel Gorman wrote: > As compaction proceeds and creates high-order blocks, the free list > search gets less efficient as the larger blocks are used as compaction > targets. Eventually, the larger blocks will be behind the migration > scanner for partially migrated pageblocks and the search fails. This > patch round-robins what orders are searched so that larger blocks can be > ignored and find smaller blocks that can be used as migration targets. > > The overall impact was small on 1-socket but it avoids corner cases where > the migration/free scanners meet prematurely or situations where many of > the pageblocks encountered by the free scanner are almost full instead of > being properly packed. Previous testing had indicated that without this > patch there were occasional large spikes in the free scanner without this > patch. By co-incidence, the 2-socket results showed a 54% reduction in > the free scanner but will not be universally true. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka