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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 4CF54C433E9 for ; Fri, 22 Jan 2021 10:35:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03582239EF for ; Fri, 22 Jan 2021 10:35:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728025AbhAVKdn (ORCPT ); Fri, 22 Jan 2021 05:33:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727051AbhAVJbq (ORCPT ); Fri, 22 Jan 2021 04:31:46 -0500 Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1160C0613D6 for ; Fri, 22 Jan 2021 01:31:04 -0800 (PST) Received: by mail-lj1-x235.google.com with SMTP id j3so5746853ljb.9 for ; Fri, 22 Jan 2021 01:31:04 -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=MH09kRgJ3c/VLXxR/STT+yQAdeF/xaJCGc1HwjRJZkE=; b=fTNefO3CE/8eT/BhlNZ/09hynki/eX2wQrVm/MfFHE1bga140ti86/ipN8YcUQw9YM B9IpLSBri0jWukR3BldrbG3XAFv33mgC9QOUbRNM5fXfAzg5TvIKSznftQrZxkY06pOE yYge6nxWVahSyHHyDrswV+g6c6RQo+p1G7AtujWjXiK3TkoNqMuDumACREroxnUcxCss dR0h2Kh+4RqLjGHs/q+V3BM/YNN0H4T3is16fLAJzLpvuu4g+QevunmCQ/bufxlLBMmF 1P7RLxD6mCNlkyJCWsKQynPTozih8GeYexPdcHI0l9CqZtp+bkbX9NSdMQ8ercJ0hJ2z 6hkQ== 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=MH09kRgJ3c/VLXxR/STT+yQAdeF/xaJCGc1HwjRJZkE=; b=Yr47tw4UXZfFn1lKHhchQBIMC3U2tuJfhTw5n+04C8P9E6b2LGesYDv0xNMpd+18tI A2BNTJokvLqSHpirsgQBNtam1ZKH8B7iQBOsy4/P8bU3sVApagm3BXJvssGA4w2yPm2S +QOZivAw/tlNqnfx6eDvS5jCJqB7KQiU8ls9atrjl/DWvxWGSihCRqC3nnl8XnAzXTAL yI59VFVqaeyEDVaRpO+tM2eLbPXQMxhk67yvINLNMSUFcIGcCvJJ88k0FflCxivUkwpd vaDAG1+lBO2MuAcVMufuRvpiicO6P0P7k79+t5WRP0gEwftQNyqVRuS68guYwmSb+ai9 EHJQ== X-Gm-Message-State: AOAM531+j/RX0Ncycrzi0kRS/9r8hzltZvEpTTzJEXawSdB45Fubkmgg G7ZKF4Ho4ebvAssZ5dhq57E4HRsXLaXcMlWSVlZabg== X-Google-Smtp-Source: ABdhPJwuoAdyNU35yxqzV+uohI/w2WqZwDX+hzgCxIwuBYuRu1hFfCLvJdYA3PkCm7AHOrv4KRb6WH2qjJLqDfBzAlE= X-Received: by 2002:a2e:b4d4:: with SMTP id r20mr788113ljm.445.1611307863312; Fri, 22 Jan 2021 01:31:03 -0800 (PST) MIME-Version: 1.0 References: <20210119112211.3196-1-mgorman@techsingularity.net> <20210119120220.GS3592@techsingularity.net> In-Reply-To: <20210119120220.GS3592@techsingularity.net> From: Vincent Guittot Date: Fri, 22 Jan 2021 10:30:52 +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 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 diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 808e40d0439d..c4de33574e6e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6138,7 +6138,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma #endif /* CONFIG_SCHED_SMT */ -#define sis_min_cores 2 +#define sis_min_cores 4 /* * Scan the LLC domain for idle CPUs; this is dynamically regulated by @@ -6176,8 +6176,6 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t else nr = sis_min_cores; - nr *= sched_smt_weight; - time = cpu_clock(this); } > > -- > Mel Gorman > SUSE Labs