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_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 DBBF0C4363A for ; Fri, 23 Oct 2020 17:59:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79428241A3 for ; Fri, 23 Oct 2020 17:59:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="IDaJPA5b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754111AbgJWR7t (ORCPT ); Fri, 23 Oct 2020 13:59:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754099AbgJWR7s (ORCPT ); Fri, 23 Oct 2020 13:59:48 -0400 Received: from mail-qt1-x842.google.com (mail-qt1-x842.google.com [IPv6:2607:f8b0:4864:20::842]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8ED45C0613CE for ; Fri, 23 Oct 2020 10:59:47 -0700 (PDT) Received: by mail-qt1-x842.google.com with SMTP id m65so1599333qte.11 for ; Fri, 23 Oct 2020 10:59:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=IDpHMieNXZZBIoI1fIHPCKIb5NTvidIxfCr8Im48pc4=; b=IDaJPA5bANTTSZhZyxYX2w2AIzGVuL3oCR2wpEGarXb7mxVjjtzPeh3NDdeE2f3PU2 4dnwndVV3sHqykCR8NpRg/A+VjzGqwEB3VO1+m2LbzmrRdZ6nCE7b2XiuQY0oQptNdPh X4qPu5ewGRXHxffnYOZvUuYHpTsi80BTsfx5I= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=IDpHMieNXZZBIoI1fIHPCKIb5NTvidIxfCr8Im48pc4=; b=aa8Zah72JK8XlnLELAf5yEFzC8j/L4O4uBXeNOMMcJgJE+pLZvOxgEayRPP9lcEjSY WFToRrHwnlMS6BA/vn1CMZoJePjGKrLnlppj8Lz4K1TUfHAZJGwHnK9jmq25Nmp+Er9Q IiohKty6UlKFsejXKvs3Nb3+AkO4+N4DKHmqoo6c/wLeltkgnVXLYJvb+ZVIxRh+ZeR9 MzVuXlKgGHDluqAyEQh6JoIp+4WKT+KhComoTmoggNyeaLVY7g8yikB9rckMMcMDiYzo iqOPB9FktGJV9tIyPAktxHHOYD+yu9m3xJFPB4VaIagmrhh8oMKTkiLt4Jil/FbSJBk3 KVlA== X-Gm-Message-State: AOAM533idbrS7zux7oRWsq2IcgpDiZ22NJGFaLARZ/AlPTj866ormtyr 5yACDdnUrCzX+Gxbuso/thJ+GQ== X-Google-Smtp-Source: ABdhPJyYidiNXKL8OLdU3yRDOm0JPUlJrrdRLcon0lUBYOQbJ18fEWBB5VK02l2lBtZeJ0O9ig0xHw== X-Received: by 2002:ac8:5141:: with SMTP id h1mr2008705qtn.139.1603475986754; Fri, 23 Oct 2020 10:59:46 -0700 (PDT) Received: from localhost ([2620:15c:6:411:cad3:ffff:feb3:bd59]) by smtp.gmail.com with ESMTPSA id z69sm1255839qkb.7.2020.10.23.10.59.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2020 10:59:46 -0700 (PDT) Date: Fri, 23 Oct 2020 13:59:45 -0400 From: Joel Fernandes To: Peter Zijlstra Cc: Nishanth Aravamudan , Julien Desfossez , Tim Chen , Vineeth Pillai , Aaron Lu , Aubrey Li , tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , vineeth@bitbyteword.org, Chen Yu , Christian Brauner , Agata Gruza , Antonio Gomez Iglesias , graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com, pjt@google.com, rostedt@goodmis.org, derkling@google.com, benbjiang@tencent.com, Alexandre Chartre , James.Bottomley@hansenpartnership.com, OWeisse@umich.edu, Dhaval Giani , Junaid Shahid , jsbarnes@google.com, chris.hyser@oracle.com, Vineeth Remanan Pillai , Aaron Lu , Aubrey Li , "Paul E. McKenney" , Tim Chen Subject: Re: [PATCH v8 -tip 06/26] sched: Add core wide task selection and scheduling. Message-ID: <20201023175945.GB3563800@google.com> References: <20201020014336.2076526-1-joel@joelfernandes.org> <20201020014336.2076526-7-joel@joelfernandes.org> <20201023150544.GG2974@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201023150544.GG2974@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 23, 2020 at 05:05:44PM +0200, Peter Zijlstra wrote: > On Mon, Oct 19, 2020 at 09:43:16PM -0400, Joel Fernandes (Google) wrote: > > From: Peter Zijlstra > > > > Instead of only selecting a local task, select a task for all SMT > > siblings for every reschedule on the core (irrespective which logical > > CPU does the reschedule). > > This: > > > > > During a CPU hotplug event, schedule would be called with the hotplugged > > CPU not in the cpumask. So use for_each_cpu(_wrap)_or to include the > > current cpu in the task pick loop. > > > > There are multiple loops in pick_next_task that iterate over CPUs in > > smt_mask. During a hotplug event, sibling could be removed from the > > smt_mask while pick_next_task is running. So we cannot trust the mask > > across the different loops. This can confuse the logic. Add a retry logic > > if smt_mask changes between the loops. > > isn't entirely accurate anymore, is it? Yes you are right, we need to delete this bit from the changelog. :-(. I'll go do that. thanks, - Joel