Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754573AbbFLMin (ORCPT ); Fri, 12 Jun 2015 08:38:43 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:36876 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753360AbbFLMik (ORCPT ); Fri, 12 Jun 2015 08:38:40 -0400 Date: Fri, 12 Jun 2015 14:38:36 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Thomas Gleixner , Preeti U Murthy , Christoph Lameter , Ingo Molnar , Viresh Kumar , Rik van Riel Subject: Re: [PATCH 5/8] nohz: Restart the tick from irq exit Message-ID: <20150612123835.GA29736@lerouge> References: <1434044168-23173-1-git-send-email-fweisbec@gmail.com> <1434044168-23173-6-git-send-email-fweisbec@gmail.com> <20150612073245.GO3644@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150612073245.GO3644@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1183 Lines: 23 On Fri, Jun 12, 2015 at 09:32:45AM +0200, Peter Zijlstra wrote: > On Thu, Jun 11, 2015 at 07:36:05PM +0200, Frederic Weisbecker wrote: > > Restart the tick when necessary from the irq exit path. It makes nohz > > full more flexible and allow it to piggyback the tick restart on the > > scheduler IPI in the future instead of sending a dedicated IPI that > > often doubles the scheduler IPI on task wakeup. This will require > > careful review of resched_curr() callers. > > This seems to assume schedule_ipi() callers use irq_exit(), this is > false. Indeed there will be that too. Note the current patch doesn't yet rely on schedule_ipi(), we are still using the nohz ipis. But introducing the tick restart on irq exit prepares for later piggybacking on scheduler_ipi(). I think this will involve changes on got_nohz_idle_kick(), renamed to got_nohz_kick() and include nohz full related checks to trigger the irq_enter()/exit() pair. -- 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/