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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 28397C433DB for ; Fri, 8 Jan 2021 15:15:36 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C085F238EC for ; Fri, 8 Jan 2021 15:15:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C085F238EC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=+qmV5mxLoe0ajkgLcITujC/QPQZTx94U3avlFyNgDgY=; b=sHci44xHOPSkh1aQTfR0MWOa2 HmAlH4ZRHulEe8UTAFwPR6SCiiouEHTX89F5drzCJmBIlLkZMio6nXyWZdjW9QaTmVLoWzyQva3Cr zf5yNt7k4xEQ0dSMWCh4M3VLZgM2RsFx3wMRKPkhp6tz//V71RzWcGz4TCKa00M/BK1vQxFP2S1Zw gMPLao0R/P3EySZxcP56Fsq7KLYejamNqoG5rxVEi2NBbBPlmdRpxpgIF6zHXF67qDIt6xX6ofGLD SRKnk9HaFe30J7nBm52eKZsROQshNcNG0RoRxehBCZvq8u2CV2nRgmr/06eHFwJl96TDCyygX+ZtW 05Ge/X3Cw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kxtS3-0000rc-CV; Fri, 08 Jan 2021 15:13:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kxtRe-0000pf-Dm for linux-arm-kernel@lists.infradead.org; Fri, 08 Jan 2021 15:12:55 +0000 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 24E61ED1; Fri, 8 Jan 2021 07:12:52 -0800 (PST) Received: from e123083-lin (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 88CFA3F70D; Fri, 8 Jan 2021 07:12:47 -0800 (PST) Date: Fri, 8 Jan 2021 16:12:41 +0100 From: Morten Rasmussen To: Tim Chen Subject: Re: [RFC PATCH v3 0/2] scheduler: expose the topology of clusters and add cluster scheduler Message-ID: <20210108151241.GA47324@e123083-lin> References: <20210106083026.40444-1-song.bao.hua@hisilicon.com> <737932c9-846a-0a6b-08b8-e2d2d95b67ce@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <737932c9-846a-0a6b-08b8-e2d2d95b67ce@linux.intel.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210108_101254_553854_581C3CA1 X-CRM114-Status: GOOD ( 14.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: juri.lelli@redhat.com, mark.rutland@arm.com, peterz@infradead.org, catalin.marinas@arm.com, bsegall@google.com, xuwei5@huawei.com, will@kernel.org, vincent.guittot@linaro.org, aubrey.li@linux.intel.com, linux-acpi@vger.kernel.org, mingo@redhat.com, mgorman@suse.de, valentin.schneider@arm.com, lenb@kernel.org, linuxarm@openeuler.org, rostedt@goodmis.org, prime.zeng@hisilicon.com, jonathan.cameron@huawei.com, dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org, Barry Song , gregkh@linuxfoundation.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, sudeep.holla@arm.com, tiantao6@hisilicon.com 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 Thu, Jan 07, 2021 at 03:16:47PM -0800, Tim Chen wrote: > On 1/6/21 12:30 AM, Barry Song wrote: > > ARM64 server chip Kunpeng 920 has 6 clusters in each NUMA node, and each > > cluster has 4 cpus. All clusters share L3 cache data while each cluster > > has local L3 tag. On the other hand, each cluster will share some > > internal system bus. This means cache is much more affine inside one cluster > > than across clusters. > > There is a similar need for clustering in x86. Some x86 cores could share L2 caches that > is similar to the cluster in Kupeng 920 (e.g. on Jacobsville there are 6 clusters > of 4 Atom cores, each cluster sharing a separate L2, and 24 cores sharing L3). > Having a sched domain at the L2 cluster helps spread load among > L2 domains. This will reduce L2 cache contention and help with > performance for low to moderate load scenarios. IIUC, you are arguing for the exact opposite behaviour, i.e. balancing between L2 caches while Barry is after consolidating tasks within the boundaries of a L3 tag cache. One helps cache utilization, the other communication latency between tasks. Am I missing something? IMHO, we need some numbers on the table to say which way to go. Looking at just benchmarks of one type doesn't show that this is a good idea in general. Morten _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel