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 0B327C433DF for ; Tue, 4 Aug 2020 10:45:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB8C72070A for ; Tue, 4 Aug 2020 10:45:55 +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="LioAvB/i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729673AbgHDKpv (ORCPT ); Tue, 4 Aug 2020 06:45:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726947AbgHDKpo (ORCPT ); Tue, 4 Aug 2020 06:45:44 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E23FC06174A for ; Tue, 4 Aug 2020 03:45:44 -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=w5o5IcAoNXwLVf59c401lTKK0QArdzdHQ89b1oA1ILw=; b=LioAvB/iKgUeNOGdS6342XE/WZ nRhe2eYGe9CGIXNs0McyJ7E1ly+G+Vj6Qe81zusLriWie0PCmW8m97VWpfGS/pBrEYsdW7z086s3O gKyBtV30aLLnMB5k7eOLgs0P1O/cqftYA9QcP7nFWF5eFvOpub9Dqh/ykq/tRhUl8o9+v0lq04wwM GVVcVmjdybTNg+ZoqfT+9FjtYyKuAAUdGSi5yCrN2mnMdL0S/U2VC22sbBHiqbYaA2QgIWuidATd2 FQThuaXFPax0FXVcGtokbfXJleTGWpc/qyrF5J0YfFRFIGOjHOd68m0a3xDhydCeR10lLQC9/iZS6 HCMsY0Aw==; 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 1k2uRf-00013s-Gz; Tue, 04 Aug 2020 10:45:23 +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 D8778301A66; Tue, 4 Aug 2020 12:45:20 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9C5AC2B94E749; Tue, 4 Aug 2020 12:45:20 +0200 (CEST) Date: Tue, 4 Aug 2020 12:45:20 +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 1/2] sched/topology: Allow archs to override cpu_smt_mask Message-ID: <20200804104520.GB2657@hirez.programming.kicks-ass.net> References: <20200804033307.76111-1-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200804033307.76111-1-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 09:03:06AM +0530, Srikar Dronamraju wrote: > cpu_smt_mask tracks topology_sibling_cpumask. This would be good for > most architectures. One of the users of cpu_smt_mask(), would be to > identify idle-cores. On Power9, a pair of cores can be presented by the > firmware as a big-core for backward compatibility reasons. > > In order to maintain userspace backward compatibility with previous > versions of processor, (since Power8 had SMT8 cores), Power9 onwards there > is option to the firmware to advertise a pair of SMT4 cores as a fused > cores (referred to as the big_core mode in the Linux Kernel). On Power9 > this pair shares the L2 cache as well. However, from the scheduler's point > of view, a core should be determined by SMT4. The load-balancer already > does this. Hence allow PowerPc architecture to override the default > cpu_smt_mask() to point to the SMT4 cores in a big_core mode. I'm utterly confused. Why can't you set your regular siblings mask to the smt4 thing? Who cares about the compat stuff, I thought that was an LPAR/AIX thing.