From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933399Ab3BSSVS (ORCPT ); Tue, 19 Feb 2013 13:21:18 -0500 Received: from mail-we0-f171.google.com ([74.125.82.171]:38028 "EHLO mail-we0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932858Ab3BSSVR (ORCPT ); Tue, 19 Feb 2013 13:21:17 -0500 Message-ID: <5123C299.3080005@linaro.org> Date: Tue, 19 Feb 2013 19:21:13 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Thomas Gleixner CC: John Stultz , Frederic Weisbecker , Linux Kernel Mailing List , "linaro-dev >> Lists Linaro-dev" Subject: Re: [resend] Timer broadcast question References: <5123BE35.8070902@linaro.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/19/2013 07:10 PM, Thomas Gleixner wrote: > On Tue, 19 Feb 2013, Daniel Lezcano wrote: >> I am working on identifying the different wakeup sources from the >> interrupts and I have a question regarding the timer broadcast. >> >> The broadcast timer is setup to the next event and that will wake up any >> idle cpu belonging to the "broadcast cpumask", right ? >> >> The cpu which has been woken up will look for each cpu the next-event >> and send an IPI to wake it up. >> >> Although, it is possible the sender of this IPI may not be concerned by >> the timer expiration and has been woken up just for sending the IPI, right ? > > Correct. > >> If this is correct, is it possible to setup the timer irq affinity to a >> cpu which will be concerned by the timer expiration ? so we prevent an >> unnecessary wake up for a cpu. > > It is possible, but we never implemented it. > > If we go there, we want to make that conditional on a property flag, > because some interrupt controllers especially on x86 only allow to > move the affinity from interrupt context, which is pointless. Thanks Thomas for your quick answer. I will write a RFC patchset. -- Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog