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,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 85270C433E0 for ; Tue, 4 Aug 2020 10:48:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F5822070A for ; Tue, 4 Aug 2020 10:48:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YQRDXeVG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729977AbgHDKsd (ORCPT ); Tue, 4 Aug 2020 06:48:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729126AbgHDKq4 (ORCPT ); Tue, 4 Aug 2020 06:46:56 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F29AC06174A for ; Tue, 4 Aug 2020 03:46:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+6Tt80sUg+tg0PdE7s0Kuf5aRtc3dDNucVqs4QUfFJo=; b=YQRDXeVGnrpdvgOV9toahm8icy oY5/5JySL/IwyPGKSuJ94/W3EiqpEYNbwAS2+Afrhvcq3qTwJfxbD803u4gx1jxnZ7n0/hlKb6sqJ 5d1+q5DC0NTdCUs2yIv4/sQQ/VOjPuaN4GqytK6eKOrLx2jtNY1DjgiurB/UcJeD/PxGqsrO1iN0R qF43d+qNaJ9uw73bDhLTCXEPiltwEzF2GFgA+ErH8g1/0yQaw3QLrEmQMVABdQSBIpn8nWKz8ieRn XxOK8EJOu9X+T6284ZuLrUq2Qx+QIYuXbL8/QJm4CFT+RSOJlYo0K2088DuiVxFABe87+qcezB/9+ aJk5+WGQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k2uSz-0001Kt-Dn; Tue, 04 Aug 2020 10:46:45 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B9F94301631; Tue, 4 Aug 2020 12:46:42 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AB51A2B94E749; Tue, 4 Aug 2020 12:46:42 +0200 (CEST) Date: Tue, 4 Aug 2020 12:46:42 +0200 From: peterz@infradead.org To: Srikar Dronamraju Cc: Ingo Molnar , LKML , Mel Gorman , Rik van Riel , Thomas Gleixner , Valentin Schneider , Vincent Guittot , Dietmar Eggemann , linuxppc-dev , Michael Ellerman , Michael Neuling , Gautham R Shenoy , Vaidyanathan Srinivasan Subject: Re: [PATCH 2/2] powerpc/topology: Override cpu_smt_mask Message-ID: <20200804104642.GC2657@hirez.programming.kicks-ass.net> References: <20200804033307.76111-1-srikar@linux.vnet.ibm.com> <20200804033307.76111-2-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200804033307.76111-2-srikar@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 04, 2020 at 09:03:07AM +0530, Srikar Dronamraju wrote: > On Power9 a pair of cores can be presented by the firmware as a big-core > for backward compatibility reasons, with 4 threads per (small) core and 8 > threads per big-core. cpu_smt_mask() should generally point to the cpu mask > of the (small)core. > > In order to maintain userspace backward compatibility (with Power8 chips in > case of Power9) in enterprise Linux systems, the topology_sibling_cpumask > has to be set to big-core. Hence override the default cpu_smt_mask() to be > powerpc specific allowing for better scheduling behaviour on Power. Why does Linux userspace care about this?