Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753559AbbDBTJR (ORCPT ); Thu, 2 Apr 2015 15:09:17 -0400 Received: from casper.infradead.org ([85.118.1.10]:38805 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752484AbbDBTJN (ORCPT ); Thu, 2 Apr 2015 15:09:13 -0400 Date: Thu, 2 Apr 2015 21:09:10 +0200 From: Peter Zijlstra To: Frederic Weisbecker Cc: LKML , Dave Jones , Thomas Gleixner , Oleg Nesterov , "Paul E . McKenney" , Ingo Molnar , Rik van Riel Subject: Re: [PATCH 2/3] context_tracking: Inherit TIF_NOHZ through forks instead of context switches Message-ID: <20150402190910.GF27490@worktop.programming.kicks-ass.net> References: <1427996365-12101-1-git-send-email-fweisbec@gmail.com> <1427996365-12101-3-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1427996365-12101-3-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 895 Lines: 20 On Thu, Apr 02, 2015 at 07:39:24PM +0200, Frederic Weisbecker wrote: > TIF_NOHZ is used by context_tracking to force syscall slow-path on every > task in order to track userspace roundtrips. As such, it must be set on > all running tasks. > > It's currently explicitly inherited through context switches. There is > no need to do it on this fast-path though. The flag could be simply > set once for all on all tasks, whether they are running or not. > > Lets do this by setting the flag to init task on early boot and let it > propagate through fork inheritance. > One must ask, what's the point of the flag if everybody must always have it set? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/