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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A415C433FE for ; Wed, 20 Apr 2022 17:00:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380820AbiDTRDj (ORCPT ); Wed, 20 Apr 2022 13:03:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380816AbiDTRDi (ORCPT ); Wed, 20 Apr 2022 13:03:38 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92DF520BC9 for ; Wed, 20 Apr 2022 10:00:50 -0700 (PDT) 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 sin.source.kernel.org (Postfix) with ESMTPS id DE164CE1F39 for ; Wed, 20 Apr 2022 17:00:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A99F1C385A1; Wed, 20 Apr 2022 17:00:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650474047; bh=IQXVmyq50eTLFr9R0yU4kcv2+J+AGruml4vdMvbhcJI=; h=Subject:To:From:Date:From; b=OWOQ1kicQahH9xnq0762DTIBiXGsbfyenIY3/eTdl28xXvEXMZ71FR0RqBd4Q9/Wr RYMk+VgcXdbfXCPaM1DkW5uyYMZAm/oO8hMB7IfI0v+MOhptNtpbRjtQv4I1t98et9 caEsXbMp9QeOpfoW2vtsGoc8BbGG08ApRVKhdwUY= Subject: patch "topology: make core_mask include at least cluster_siblings" added to driver-core-linus To: darren@os.amperecomputing.com, catalin.marinas@arm.com, dietmar.eggemann@arm.com, gregkh@linuxfoundation.org, ilkka@os.amperecomputing.com, peterz@infradead.org, rafael@kernel.org, scott@os.amperecomputing.com, song.bao.hua@hisilicon.com, stable@vger.kernel.org, sudeep.holla@arm.com, vincent.guittot@linaro.org, will@kernel.org From: Date: Wed, 20 Apr 2022 19:00:36 +0200 Message-ID: <1650474036203198@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled topology: make core_mask include at least cluster_siblings to my driver-core git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git in the driver-core-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From db1e59483dfd8d4e956575302520bb8f7e20c79b Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Mon, 11 Apr 2022 13:53:34 -0700 Subject: topology: make core_mask include at least cluster_siblings 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. Only do this if CONFIG_SCHED_CLUSTER is enabled to avoid also changing the topology (MC) when CONFIG_SCHED_CLUSTER is disabled. 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: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Cc: Catalin Marinas Cc: Will Deacon Cc: Peter Zijlstra Cc: Vincent Guittot Cc: D. Scott Phillips Cc: Ilkka Koskinen Cc: # 5.16.x Suggested-by: Barry Song Reviewed-by: Barry Song Reviewed-by: Dietmar Eggemann Acked-by: Sudeep Holla Signed-off-by: Darren Hart Link: https://lore.kernel.org/r/c8fe9fce7c86ed56b4c455b8c902982dc2303868.1649696956.git.darren@os.amperecomputing.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/arch_topology.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 1d6636ebaac5..5497c5ab7318 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -667,6 +667,15 @@ 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 (IS_ENABLED(CONFIG_SCHED_CLUSTER) && + cpumask_subset(core_mask, &cpu_topology[cpu].cluster_sibling)) + core_mask = &cpu_topology[cpu].cluster_sibling; + return core_mask; } -- 2.35.3