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[23.128.96.18]) by mx.google.com with ESMTP id 17si281717ilj.19.2021.05.19.11.20.30; Wed, 19 May 2021 11:20:42 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350175AbhERPMv (ORCPT + 99 others); Tue, 18 May 2021 11:12:51 -0400 Received: from foss.arm.com ([217.140.110.172]:54428 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350032AbhERPLM (ORCPT ); Tue, 18 May 2021 11:11:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E2C66ED1; Tue, 18 May 2021 08:09:53 -0700 (PDT) Received: from e120325.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6CA8C3F73B; Tue, 18 May 2021 08:09:51 -0700 (PDT) Date: Tue, 18 May 2021 16:09:48 +0100 From: Beata Michalska To: Vincent Guittot Cc: linux-kernel , Peter Zijlstra , Ingo Molnar , Juri Lelli , Valentin Schneider , Dietmar Eggemann , "corbet@lwn.net" , Randy Dunlap , Linux Doc Mailing List Subject: Re: [PATCH v4 1/3] sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag Message-ID: <20210518150947.GC3993@e120325.cambridge.arm.com> References: <1621239831-5870-1-git-send-email-beata.michalska@arm.com> <1621239831-5870-2-git-send-email-beata.michalska@arm.com> <20210518142746.GA3993@e120325.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 18, 2021 at 04:53:09PM +0200, Vincent Guittot wrote: > On Tue, 18 May 2021 at 16:27, Beata Michalska wrote: > > > > On Tue, May 18, 2021 at 03:39:27PM +0200, Vincent Guittot wrote: > > > On Mon, 17 May 2021 at 10:24, Beata Michalska wrote: > > > > > > > > Introducing new, complementary to SD_ASYM_CPUCAPACITY, sched_domain > > > > topology flag, to distinguish between shed_domains where any CPU > > > > capacity asymmetry is detected (SD_ASYM_CPUCAPACITY) and ones where > > > > a full range of CPU capacities is visible to all domain members > > > > (SD_ASYM_CPUCAPACITY_FULL). > > > > > > I'm not sure about what you want to detect: > > > > > > Is it a sched_domain level with a full range of cpu capacity, i.e. > > > with at least 1 min capacity and 1 max capacity ? > > > or do you want to get at least 1 cpu of each capacity ? > > That would be at least one CPU of each available capacity within given domain, > > so full -set- of available capacities within a domain. > > Would be good to add the precision. Will do. > > Although I'm not sure if that's the best policy compared to only > getting the range which would be far simpler to implement. > Do you have some topology example ? An example from second patch from the series: DIE [ ] MC [ ][ ] CPU [0] [1] [2] [3] [4] [5] [6] [7] Capacity |.....| |.....| |.....| |.....| L M B B Where: arch_scale_cpu_capacity(L) = 512 arch_scale_cpu_capacity(M) = 871 arch_scale_cpu_capacity(B) = 1024 which could also look like: DIE [ ] MC [ ][ ] CPU [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] Capacity |.....| |.....| |.....| |.....| |.....| L M B L B Considering only range would mean loosing the 2 (M) CPUs out of sight for feec in some cases. --- BR. B > > > > > > > > > > --- > > BR > > B. > > > > > > > > > > > > > > With the distinction between full and partial CPU capacity asymmetry, > > > > brought in by the newly introduced flag, the scope of the original > > > > SD_ASYM_CPUCAPACITY flag gets shifted, still maintaining the existing > > > > behaviour when one is detected on a given sched domain, allowing > > > > misfit migrations within sched domains that do not observe full range > > > > of CPU capacities but still do have members with different capacity > > > > values. It loses though it's meaning when it comes to the lowest CPU > > > > asymmetry sched_domain level per-cpu pointer, which is to be now > > > > denoted by SD_ASYM_CPUCAPACITY_FULL flag. > > > > > > > > Signed-off-by: Beata Michalska > > > > Reviewed-by: Valentin Schneider > > > > --- > > > > include/linux/sched/sd_flags.h | 10 ++++++++++ > > > > 1 file changed, 10 insertions(+) > > > > > > > > diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h > > > > index 34b21e9..57bde66 100644 > > > > --- a/include/linux/sched/sd_flags.h > > > > +++ b/include/linux/sched/sd_flags.h > > > > @@ -91,6 +91,16 @@ SD_FLAG(SD_WAKE_AFFINE, SDF_SHARED_CHILD) > > > > SD_FLAG(SD_ASYM_CPUCAPACITY, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > > > > > > > > /* > > > > + * Domain members have different CPU capacities spanning all unique CPU > > > > + * capacity values. > > > > + * > > > > + * SHARED_PARENT: Set from the topmost domain down to the first domain where > > > > + * all available CPU capacities are visible > > > > + * NEEDS_GROUPS: Per-CPU capacity is asymmetric between groups. > > > > + */ > > > > +SD_FLAG(SD_ASYM_CPUCAPACITY_FULL, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > > > > + > > > > +/* > > > > * Domain members share CPU capacity (i.e. SMT) > > > > * > > > > * SHARED_CHILD: Set from the base domain up until spanned CPUs no longer share > > > > -- > > > > 2.7.4 > > > >