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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 B352EC433DB for ; Fri, 22 Jan 2021 13:24:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82BD023437 for ; Fri, 22 Jan 2021 13:24:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727869AbhAVNYA (ORCPT ); Fri, 22 Jan 2021 08:24:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727442AbhAVNXs (ORCPT ); Fri, 22 Jan 2021 08:23:48 -0500 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F8FFC06174A for ; Fri, 22 Jan 2021 05:22:55 -0800 (PST) Received: by mail-lj1-x22c.google.com with SMTP id x23so6480918lji.7 for ; Fri, 22 Jan 2021 05:22:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1dlLJO6jimId6EJsncVivsPX+l64PBMqOs921XyJpHA=; b=c00xADeTOhigVGdMbnIU9Cl9YxVuBfvlEyv2hzJg9kl+WSIDiSBDnT+aCpEsFZtBBv 5jxVvHv7OZafaNg41JCUGIP1QVbZf+Zme9kKfZ4tHSiUXDDtQ21d4j/E3Cgx80eEmx3E CVK7eptZWiy5w2+6V8UhLilqMCp7cjJ5qMwJzWJ71MuN9hIJUqfcPOqTm+MQRIQJQjdT L1peGn+mvievW5U+/NZB2efL4aZMtxoJP7N1wZEQIgdUgSMaQcFZ2V0FDt5GbAKOSMSB 3X6G3cgS3al19s58GyD5Mr1ozFjhX0oQoMbuzHPC9eO4mEf2zdsbg3osmkkMp7/A7PLQ 3dEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1dlLJO6jimId6EJsncVivsPX+l64PBMqOs921XyJpHA=; b=RZqWEdjYUL4zLsGc81q3eJa33EXGzUgAEUIN4wG39tUqpaGt08vyOhkDO8AV7SEy9C 3QXirATJU8ixr0oxOBD4N1k/fICX/LAyxvoJDSzrW9bS6n+gZqjzeDV6xpueua+4Vo05 rKJTfQJdBwor+u8kTX1EfqG2TAKnSBYHZ3Iul1gPWSO6EDQPX6gZF7QRwqJvjsO9Edht ZgCrYPn6EW1JBazarpTrKQsA9RBSNMA+KZkgz5eb9wxeG2qDPuRf0Jy6N/zMP8uY3zNh H5PGsrt5X67z2GBz1UYSjnW5hhMXcqihjX91ovBkC71f5QsT3t4HkTsuoHNZEw/Ruf4D sSOg== X-Gm-Message-State: AOAM5322vcBPnUiFfXBfFoiwXqR9OUkrZsR2qCL8YmjDNk3vErRdzkWK WaoruWNA71xeBVlpccWXYiMtS3Eo0Hy2P7EXPnrVUg== X-Google-Smtp-Source: ABdhPJwxt7JID1hIl/F5HBEOcsbDE0mB6FQghCfYyuyAC6L43CU/08jyyt/UjTIUCfbft2K6QRtqe+QhpFaQ5NhoCQo= X-Received: by 2002:a2e:b4d4:: with SMTP id r20mr1253380ljm.445.1611321773620; Fri, 22 Jan 2021 05:22:53 -0800 (PST) MIME-Version: 1.0 References: <20210119112211.3196-1-mgorman@techsingularity.net> <20210119120220.GS3592@techsingularity.net> <20210122101451.GV3592@techsingularity.net> In-Reply-To: <20210122101451.GV3592@techsingularity.net> From: Vincent Guittot Date: Fri, 22 Jan 2021 14:22:42 +0100 Message-ID: Subject: Re: [PATCH v3 0/5] Scan for an idle sibling in a single pass To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Li Aubrey , Qais Yousef , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Jan 2021 at 11:14, Mel Gorman wrote: > > On Fri, Jan 22, 2021 at 10:30:52AM +0100, Vincent Guittot wrote: > > Hi Mel, > > > > On Tue, 19 Jan 2021 at 13:02, Mel Gorman wrote: > > > > > > On Tue, Jan 19, 2021 at 12:33:04PM +0100, Vincent Guittot wrote: > > > > On Tue, 19 Jan 2021 at 12:22, Mel Gorman wrote: > > > > > > > > > > Changelog since v2 > > > > > o Remove unnecessary parameters > > > > > o Update nr during scan only when scanning for cpus > > > > > > > > Hi Mel, > > > > > > > > I haven't looked at your previous version mainly because I'm chasing a > > > > performance regression on v5.11-rcx which prevents me from testing the > > > > impact of your patchset on my !SMT2 system. > > > > Will do this as soon as this problem is fixed > > > > > > > > > > Thanks, that would be appreciated as I do not have access to a !SMT2 > > > system to do my own evaluation. > > > > I have been able to run tests with your patchset on both large arm64 > > SMT4 system and small arm64 !SMT system and patch 3 is still a source > > of regression on both. Decreasing min number of loops to 2 instead of > > 4 and scaling it with smt weight doesn't seem to be a good option as > > regressions disappear when I remove them as I tested with the patch > > below > > > > hackbench -l 2560 -g 1 on 8 cores arm64 > > v5.11-rc4 : 1.355 (+/- 7.96) > > + sis improvement : 1.923 (+/- 25%) > > + the patch below : 1.332 (+/- 4.95) > > > > hackbench -l 2560 -g 256 on 8 cores arm64 > > v5.11-rc4 : 2.116 (+/- 4.62%) > > + sis improvement : 2.216 (+/- 3.84%) > > + the patch below : 2.113 (+/- 3.01%) > > > > So starting with a min of 2 loops instead of 4 currently and scaling > > nr loop with smt weight doesn't seem to be a good option and we should > > remove it for now > > > > Ok > > Note that this is essentially reverting the patch. As you remove "nr *= > sched_smt_weight", the scan is no longer proportional to cores, it's Yes. My goal above was to narrow the changes only to lines that generate the regressions but i agree that removing patch 3 is the right solution > proportial to logical CPUs and the rest of the patch and changelog becomes > meaningless. On that basis, I'll queue tests over the weekend that remove > this patch entirely and keep the CPU scan as a single pass. > > -- > Mel Gorman > SUSE Labs