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=-5.8 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 21855C2D0E4 for ; Tue, 24 Nov 2020 08:17:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7A4320708 for ; Tue, 24 Nov 2020 08:17:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="VYsntT46" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730458AbgKXIRg (ORCPT ); Tue, 24 Nov 2020 03:17:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730447AbgKXIRf (ORCPT ); Tue, 24 Nov 2020 03:17:35 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55E5AC0613CF for ; Tue, 24 Nov 2020 00:17:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=ZyExhNch12p/Hcf7krqTIV0ABzoKgV0CWL75KJBPvXE=; b=VYsntT46dXn0wMY+icj6UFPlZ1 sUZkxMaH3PWgi/+2vRcVnqUMHNpuPwEW5qS6ltRzAqShDF5qwf09asI0ENY08G7ugxgXoVhiaeYw/ /4S+O9IoPDT8Rr3LwB/gFZatuOnOF4hoUnFsgbwRCT9S644y26gIsd2UvcCBGnG4HZsm02AZHXH+3 sLeedJWHZA8ToXSJmG4GCtWmY6ZgAGQwbXvP9+9WlplaRTZK4NFtaDgSBQXiPfS0ymBgCNj31d/1d /B9HQTB64cnslpVo0BhrbR7n4S1p4StFQuOFa5AnmX3TX3TsLGYT4x1jZ/RbdCkFrmiVEh6yA91f9 QqHXwaoQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1khTUq-00034C-15; Tue, 24 Nov 2020 08:16:20 +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 D464030280E; Tue, 24 Nov 2020 09:16:17 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AE4B924C2AFCE; Tue, 24 Nov 2020 09:16:17 +0100 (CET) Date: Tue, 24 Nov 2020 09:16:17 +0100 From: Peter Zijlstra To: Balbir Singh Cc: "Joel Fernandes (Google)" , 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, Ben Segall , Josh Don , Hao Luo , Tom Lendacky , Aubrey Li , "Paul E. McKenney" , Tim Chen Subject: Re: [PATCH -tip 04/32] sched: Core-wide rq->lock Message-ID: <20201124081617.GT3021@hirez.programming.kicks-ass.net> References: <20201117232003.3580179-1-joel@joelfernandes.org> <20201117232003.3580179-5-joel@joelfernandes.org> <20201122091152.GB110669@balbir-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201122091152.GB110669@balbir-desktop> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 22, 2020 at 08:11:52PM +1100, Balbir Singh wrote: > On Tue, Nov 17, 2020 at 06:19:34PM -0500, Joel Fernandes (Google) wrote: > > From: Peter Zijlstra > > > > Introduce the basic infrastructure to have a core wide rq->lock. > > > > Reading through the patch, it seems like all the CPUs have to be > running with sched core enabled/disabled? Is it possible to have some > cores with core sched disabled? Yep, patch even says so: + * XXX entirely possible to selectively enable cores, don't bother for now. > I don't see a strong use case for it, > but I am wondering if the design will fall apart if that assumption is > broken? The use-case I have is not using stop-machine. That is, stopping a whole core at a time, instead of the whole sodding machine. It's on the todo list *somewhere*....