From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753158AbdEPNLC (ORCPT ); Tue, 16 May 2017 09:11:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:40276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752172AbdEPNK4 (ORCPT ); Tue, 16 May 2017 09:10:56 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E338239BA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Tue, 16 May 2017 09:10:53 -0400 From: Steven Rostedt To: Juri Lelli Cc: Byungchul Park , 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: <20170516091053.5f0868b5@gandalf.local.home> In-Reply-To: <20170516103241.xony5rtmqi66gczy@e106622-lin> 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> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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. -- Steve