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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 104A9C433F5 for ; Tue, 8 Mar 2022 10:39:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ZXSXYibBK6AryUHJ/BWu/eqyE3jHwrkZdk4KvV6gA/Y=; b=cy7kmtzFQDTutl Ho7X2ZAhLf69Y+6mSz9tmMQoWupnVsqMBqc6Ufhvfud4dafuR2pwtOfGLYCbRwc/nhuwAZlc++jBD vjyGiIUEy1FCGcHHpCggnwVDeJplsZstIv7PjrYexdmjOK/ldMd20AfkcYjxT7D8yEll3tNwtNDCX //WbS3Fy/Xzb3XxmC8qZMzmShIqJwBwzcwCcFhqPWp+MhbEbtDq6KXzebQmFCC0NohL84Qm8KKruv fLvdTa+ciGr7WbODaRtbit8P++eIK8Ks+acTCx7lJe0XxsYx7WgOCPS4wwKSaQ9ocJHscqpamGjPl kZ82A6toIdCC5FqazV2w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRXEU-003vnu-9W; Tue, 08 Mar 2022 10:38:24 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRX6i-003saF-PE for linux-arm-kernel@lists.infradead.org; Tue, 08 Mar 2022 10:30:22 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 640656157E; Tue, 8 Mar 2022 10:30:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C1DBC340EF; Tue, 8 Mar 2022 10:30:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646735418; bh=E6G3HiPLRyrOj03X2ujBXJMTzrUxMjwNhkXg21CG+U8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M1oThiuofqh3xeFKZQaytRfDhYBezMDPsbC39YerDdHh4F5nK9JK8QrEQH8Xxzizj mdWhdifioc/a36RrkAwGUv65W9qE7o1eN1jkLp4RWCDC7Jgl1oxN7iCGMQBhtxphnF fYFXZ+SB2c1J3cTZ+CHANzEIThoY+23DDUbftNvRq9GlTi6F7Kzjw08oaqeJd7FfFK TpsQGsL5y4USLmVhRnavuC4O3JyMGFn5rDAlu9ec98fguQ2Q/S3mQKMf4yN7zdKSYI wRRCQsLdmNRI831GB4+IYcSC9ty4y3TKUD87YJlxwfyY7EKo3+PUg9acrBX54Kmh5Y n5f8EsboETDvw== Date: Tue, 8 Mar 2022 10:30:12 +0000 From: Will Deacon To: Darren Hart Cc: LKML , Linux Arm , Sudeep Holla , Greg Kroah-Hartman , "Rafael J. Wysocki" , Catalin Marinas , Peter Zijlstra , Vincent Guittot , Barry Song , Valentin Schneider , "D . Scott Phillips" , Ilkka Koskinen , stable@vger.kernel.org Subject: Re: [PATCH v3] topology: make core_mask include at least cluster_siblings Message-ID: <20220308103012.GA31267@willie-the-truck> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220308_023020_933294_09593A83 X-CRM114-Status: GOOD ( 27.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Mar 04, 2022 at 09:01:36AM -0800, Darren Hart wrote: > Ampere Altra defines CPU clusters in the ACPI PPTT. They share a Snoop > Control Unit, but have no shared CPU-side last level cache. > > cpu_coregroup_mask() will return a cpumask with weight 1, while > cpu_clustergroup_mask() will return a cpumask with weight 2. > > As a result, build_sched_domain() will BUG() once per CPU with: > > BUG: arch topology borken > the CLS domain not a subset of the MC domain > > The MC level cpumask is then extended to that of the CLS child, and is > later removed entirely as redundant. This sched domain topology is an > improvement over previous topologies, or those built without > SCHED_CLUSTER, particularly for certain latency sensitive workloads. > With the current scheduler model and heuristics, this is a desirable > default topology for Ampere Altra and Altra Max system. > > Rather than create a custom sched domains topology structure and > introduce new logic in arch/arm64 to detect these systems, update the > core_mask so coregroup is never a subset of clustergroup, extending it > to cluster_siblings if necessary. > > This has the added benefit over a custom topology of working for both > symmetric and asymmetric topologies. It does not address systems where > the cluster topology is above a populated mc topology, but these are not > considered today and can be addressed separately if and when they > appear. > > The final sched domain topology for a 2 socket Ampere Altra system is > unchanged with or without CONFIG_SCHED_CLUSTER, and the BUG is avoided: > > For CPU0: > > CONFIG_SCHED_CLUSTER=y > CLS [0-1] > DIE [0-79] > NUMA [0-159] > > CONFIG_SCHED_CLUSTER is not set > DIE [0-79] > NUMA [0-159] > > Cc: Sudeep Holla > Cc: Greg Kroah-Hartman > Cc: "Rafael J. Wysocki" > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Vincent Guittot > Cc: Barry Song > Cc: Valentin Schneider > Cc: D. Scott Phillips > Cc: Ilkka Koskinen > Cc: # 5.16.x > Suggested-by: Barry Song > Signed-off-by: Darren Hart > --- > v1: Drop MC level if coregroup weight == 1 > v2: New sd topo in arch/arm64/kernel/smp.c > v3: No new topo, extend core_mask to cluster_siblings > > drivers/base/arch_topology.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 976154140f0b..a96f45db928b 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -628,6 +628,14 @@ const struct cpumask *cpu_coregroup_mask(int cpu) > core_mask = &cpu_topology[cpu].llc_sibling; > } > > + /* > + * For systems with no shared cpu-side LLC but with clusters defined, > + * extend core_mask to cluster_siblings. The sched domain builder will > + * then remove MC as redundant with CLS if SCHED_CLUSTER is enabled. > + */ > + if (cpumask_subset(core_mask, &cpu_topology[cpu].cluster_sibling)) > + core_mask = &cpu_topology[cpu].cluster_sibling; > + Sudeep, Vincent, are you happy with this now? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel