From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760664AbdEWBLm (ORCPT ); Mon, 22 May 2017 21:11:42 -0400 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:38106 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758691AbdEWBLk (ORCPT ); Mon, 22 May 2017 21:11:40 -0400 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Tue, 23 May 2017 10:11:23 +0900 From: Byungchul Park To: Steven Rostedt Cc: Juri Lelli , peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, bristot@redhat.com, kernel-team@lge.com Subject: Re: [PATCH v4 1/5] sched/deadline: Refer to cpudl.elements atomically Message-ID: <20170523011123.GH28017@X58A-UD3R> References: <1494568129-9985-1-git-send-email-byungchul.park@lge.com> <1494568129-9985-2-git-send-email-byungchul.park@lge.com> <20170512102530.50b85979@gandalf.local.home> <20170516065223.GA24127@X58A-UD3R> <20170516103241.xony5rtmqi66gczy@e106622-lin> <20170516091053.5f0868b5@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170516091053.5f0868b5@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 16, 2017 at 09:10:53AM -0400, Steven Rostedt wrote: > On Tue, 16 May 2017 11:32:41 +0100 > Juri Lelli wrote: > > > > Not sure, but if we are going to retry a lot it might be better off to > > put proper locking instead? We could also simply bail out when we notice > > Actually, locking can make it much worse. I've been playing with RT on > boxes with 240 cores (with HT turned off!), and *any* locks in the > scheduler can cause huge contention. OK. I give up patches adding locks here. Thank you for explaning why you did not write code in such a way like mine. > > that something is changed under our feet. I'd say (again :) we might > > first want to understand (with some numbers) how bad the problem is and > > then fix it. I guess numbers might also help us to better understand > > what the best fix is? > > Exactly. I haven't seen any numbers. Yes, it is not perfect, but we > don't know how unperfect it is. Numbers will help to know if there is > even a problem or not with the current solution. Yes. I am also curious about the number and want to check the number, but it's not easy to me since I don't have such a big machine. For now, only thing I can do is to skip the patch. Thank you very much for all of your opinions.