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=-3.8 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 0D1A6C433E7 for ; Mon, 19 Oct 2020 13:49:38 +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 89714222BA for ; Mon, 19 Oct 2020 13:49:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="iLoQWR43" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 89714222BA 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:MIME-Version:Message-ID:Date:In-reply-to:Subject:To: From:References:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/ppANsOnpDB3g0a7E9c7N0DdSABR2aumElWERyBZkNQ=; b=iLoQWR43eOD6bRNh+0ofSPzmf +1ZzjkmhA1HoFzzaPMP5yQT3y5I/QRsyHzOuIJiDzA8Xx/vuqLHGsyG8KbUllp293m+Od0LAoAhCE 5Uyt4YPVnTgB3NYZlk/tk8SDwO7QRhahaDftw+fCcs0HG+1CcXqEretpWfho9LVDazuiWqmd4k/Ie uf/LZAEGDIupoo286SMus/fOOARD6CfCaSSoD0mxA3Ismu1/OauolSTI5+WQEV7s4riFzDBszuLai 1V3GrbYP2dxrL7FuqiS+vvf0a9VuwG2MMNMet6x4iqK9TdNDhO3/HwZD1X5BsicQBragmhliGwkuN 0T+3tgAig==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUVWH-0002KN-7C; Mon, 19 Oct 2020 13:48:13 +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 1kUVWF-0002JW-9I for linux-arm-kernel@lists.infradead.org; Mon, 19 Oct 2020 13:48:12 +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 5E5A1D6E; Mon, 19 Oct 2020 06:48:08 -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 7ACF33F66E; Mon, 19 Oct 2020 06:48:06 -0700 (PDT) References: <20201016152702.1513592-1-Jonathan.Cameron@huawei.com> <20201019103522.GK2628@hirez.programming.kicks-ass.net> <20201019123226.00006705@Huawei.com> <20201019131052.GC8004@e123083-lin> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Morten Rasmussen Subject: Re: [RFC PATCH] topology: Represent clusters of CPUs within a die. In-reply-to: <20201019131052.GC8004@e123083-lin> Date: Mon, 19 Oct 2020 14:48:02 +0100 Message-ID: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201019_094811_382269_53531529 X-CRM114-Status: GOOD ( 15.88 ) 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: Len Brown , Sudeep Holla , Peter Zijlstra , Greg Kroah-Hartman , x86@kernel.org, guohanjun@huawei.com, linux-kernel@vger.kernel.org, Jeremy Linton , linuxarm@huawei.com, Brice Goglin , linux-acpi@vger.kernel.org, Jonathan Cameron , Will Deacon , linux-arm-kernel@lists.infradead.org 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 +Cc Jeremy On 19/10/20 14:10, Morten Rasmussen wrote: > Hi Jonathan, > The problem I see is that the benefit of keeping tasks together due to > the interconnect layout might vary significantly between systems. So if > we introduce a new cpumask for cluster it has to have represent roughly > the same system properties otherwise generic software consuming this > information could be tricked. > > If there is a provable benefit of having interconnect grouping > information, I think it would be better represented by a distance matrix > like we have for NUMA. > > Morten That's my queue to paste some of that stuff I've been rambling on and off about! With regards to cache / interconnect layout, I do believe that if we want to support in the scheduler itself then we should leverage some distance table rather than to create X extra scheduler topology levels. I had a chat with Jeremy on the ACPI side of that sometime ago. IIRC given that SLIT gives us a distance value between any two PXM, we could directly express core-to-core distance in that table. With that (and if that still lets us properly discover NUMA node spans), we could let the scheduler build dynamic NUMA-like topology levels representing the inner quirks of the cache / interconnect layout. It's mostly pipe dreams for now, but there seems to be more and more hardware where that would make sense; somewhat recently the PowerPC guys added something to their arch-specific code in that regards. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel