From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759219AbbLBRPb (ORCPT ); Wed, 2 Dec 2015 12:15:31 -0500 Received: from casper.infradead.org ([85.118.1.10]:33699 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752037AbbLBRP1 (ORCPT ); Wed, 2 Dec 2015 12:15:27 -0500 Date: Wed, 2 Dec 2015 18:15:21 +0100 From: Peter Zijlstra To: Frederic Weisbecker Cc: Chris Metcalf , LKML , Thomas Gleixner , Luiz Capitulino , Christoph Lameter , Ingo Molnar , Viresh Kumar , Rik van Riel Subject: Re: [PATCH 3/7] perf: Migrate perf to use new tick dependency mask model Message-ID: <20151202171521.GU3816@twins.programming.kicks-ass.net> References: <1447424529-13671-1-git-send-email-fweisbec@gmail.com> <1447424529-13671-4-git-send-email-fweisbec@gmail.com> <56548E15.5050004@ezchip.com> <20151125123428.GD16609@lerouge> <20151202161758.GS3816@twins.programming.kicks-ass.net> <20151202170313.GB16408@lerouge> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151202170313.GB16408@lerouge> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2015 at 06:03:14PM +0100, Frederic Weisbecker wrote: > Right, I can do either that or I can move the dependency to the CPU level > and count nr_freq to the cpu_ctx when any ctx gets scheduled in/out. Then > everytime we inc and nr_freq == 1, we set the dependency (all that should > be serialized as it only happens locally). Doing it per CPU would, as you say, add accounting crap to the context switch path. Now given that context switches with perf enabled are already silly expensive that might just fall away into the noise.