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[209.132.180.67]) by mx.google.com with ESMTP id d185si7830705oif.234.2020.03.23.10.10.28; Mon, 23 Mar 2020 10:10:43 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727517AbgCWRKI (ORCPT + 99 others); Mon, 23 Mar 2020 13:10:08 -0400 Received: from foss.arm.com ([217.140.110.172]:52208 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727201AbgCWRKI (ORCPT ); Mon, 23 Mar 2020 13:10:08 -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 31C381FB; Mon, 23 Mar 2020 10:10:07 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 456F53F7C3; Mon, 23 Mar 2020 10:10:06 -0700 (PDT) References: <20200311183320.19186-1-valentin.schneider@arm.com> <20200311183320.19186-2-valentin.schneider@arm.com> <20200323134234.GD6103@e123083-lin> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Morten Rasmussen Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH 1/3] sched/topology: Split out SD_* flags declaration to its own file In-reply-to: <20200323134234.GD6103@e123083-lin> Date: Mon, 23 Mar 2020 17:10:00 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Morten, Just as a heads-up, I think those changes would better fit 2/3, or be in their own patch. 1/3 is just a straight up code move, with no changes to the existing comments. On Mon, Mar 23 2020, Morten Rasmussen wrote: > On Wed, Mar 11, 2020 at 06:33:18PM +0000, Valentin Schneider wrote: >> diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h >> new file mode 100644 >> index 000000000000..685bbe736945 >> --- /dev/null >> +++ b/include/linux/sched/sd_flags.h >> @@ -0,0 +1,33 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * sched-domains (multiprocessor balancing) flag declarations. >> + */ >> + >> +/* Balance when about to become idle */ >> +SD_FLAG(SD_BALANCE_NEWIDLE, 0) >> +/* Balance on exec */ >> +SD_FLAG(SD_BALANCE_EXEC, 1) >> +/* Balance on fork, clone */ >> +SD_FLAG(SD_BALANCE_FORK, 2) >> +/* Balance on wakeup */ >> +SD_FLAG(SD_BALANCE_WAKE, 3) >> +/* Wake task to waking CPU */ >> +SD_FLAG(SD_WAKE_AFFINE, 4) > > Isn't it more like: "Consider waking task on waking CPU"? > > IIRC, with this flag set the wake-up can happen either near prev_cpu or > this_cpu. > Right, it's not a hard guarantee. >> +/* Domain members have different CPU capacities */ >> +SD_FLAG(SD_ASYM_CPUCAPACITY, 5) >> +/* Domain members share CPU capacity */ >> +SD_FLAG(SD_SHARE_CPUCAPACITY, 6) > > Perhaps add +" (SMT)" to the comment to help the uninitiated > understanding it a bit easier? > Sounds good. >> +/* Domain members share power domain */ >> +SD_FLAG(SD_SHARE_POWERDOMAIN, 7) > > This flag is set only by 32-bit arm and has never had any effect. I > think it was the beginning of something years ago that hasn't > progressed. Perhaps we can remove it now? > Right, I don't think I've seen anything recent that uses that flag. >> +/* Domain members share CPU pkg resources */ >> +SD_FLAG(SD_SHARE_PKG_RESOURCES, 8) > > +" (e.g. caches)" ? > Agreed! I actually already have that one in 2/3. >> +/* Only a single load balancing instance */ >> +SD_FLAG(SD_SERIALIZE, 9) >> +/* Place busy groups earlier in the domain */ >> +SD_FLAG(SD_ASYM_PACKING, 10) > > Place busy _tasks_ earlier in the domain? > Ack. > It is a bit unclear what 'earlier' means here but since the packing > ordering can actually be defined by the architecture, we can't be much > more specific I guess. > This probably dates back to when ASYM_PACKING was really just for bubbling tasks up to the first CPU of each core, and hasn't been changed when the asym_priority thing was introduced. I can add a pointer to that. > Morten