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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 513CAC43387 for ; Tue, 18 Dec 2018 09:55:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2932521841 for ; Tue, 18 Dec 2018 09:55:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726501AbeLRJzQ (ORCPT ); Tue, 18 Dec 2018 04:55:16 -0500 Received: from outbound-smtp12.blacknight.com ([46.22.139.17]:42734 "EHLO outbound-smtp12.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726397AbeLRJzO (ORCPT ); Tue, 18 Dec 2018 04:55:14 -0500 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp12.blacknight.com (Postfix) with ESMTPS id 6AB6B1C2222 for ; Tue, 18 Dec 2018 09:55:12 +0000 (GMT) Received: (qmail 17620 invoked from network); 18 Dec 2018 09:55:12 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[37.228.229.96]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 18 Dec 2018 09:55:12 -0000 Date: Tue, 18 Dec 2018 09:55:10 +0000 From: Mel Gorman 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 Subject: Re: [PATCH 06/14] mm, migrate: Immediately fail migration of a page with no migration handler Message-ID: <20181218095510.GJ29005@techsingularity.net> References: <20181214230310.572-1-mgorman@techsingularity.net> <20181214230310.572-7-mgorman@techsingularity.net> <0ef5c1d0-1853-8fdb-1a68-7482297cb802@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <0ef5c1d0-1853-8fdb-1a68-7482297cb802@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 18, 2018 at 10:06:31AM +0100, Vlastimil Babka wrote: > On 12/15/18 12:03 AM, Mel Gorman wrote: > > Pages with no migration handler use a fallback hander which sometimes > > works and sometimes persistently fails such as blockdev pages. Migration > > will retry a number of times on these persistent pages which is wasteful > > during compaction. This patch will fail migration immediately unless the > > caller is in MIGRATE_SYNC mode which indicates the caller is willing to > > wait while being persistent. > > Right. > > > This is not expected to help THP allocation success rates but it does > > reduce latencies slightly. > > > > 1-socket thpfioscale > > 4.20.0-rc6 4.20.0-rc6 > > noreserved-v1r4 failfast-v1r4 > > Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* > > Amean fault-both-3 2276.15 ( 0.00%) 3867.54 * -69.92%* > > This is rather weird. > Fault latency is extremely variable and there can be very large outliers that skew the mean (the full report includes quartiles but it makes for an excessive changelog). It can be down to luck about how often the migrate scanner advances and how often it gets reset. For this series, it'll not be unusual to see jitter in the latencies for individual patches that will not get nailed down reliably until later in the series. The alternative is massive patches that do multiple things which will look nice in changelogs and be horrible to review. > > Amean fault-both-5 4992.20 ( 0.00%) 5313.20 ( -6.43%) > > Amean fault-both-7 7373.30 ( 0.00%) 7039.11 ( 4.53%) > > Amean fault-both-12 11911.52 ( 0.00%) 11328.29 ( 4.90%) > > Amean fault-both-18 17209.42 ( 0.00%) 16455.34 ( 4.38%) > > Amean fault-both-24 20943.71 ( 0.00%) 20448.94 ( 2.36%) > > Amean fault-both-30 22703.00 ( 0.00%) 21655.07 ( 4.62%) > > Amean fault-both-32 22461.41 ( 0.00%) 21415.35 ( 4.66%) > > > > The 2-socket results are not materially different. Scan rates are > > similar as expected. > > > > Signed-off-by: Mel Gorman > > Acked-by: Vlastimil Babka > Thanks. -- Mel Gorman SUSE Labs