From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederic Weisbecker Subject: Re: [patch] rt: sysprof hrtimer fix Date: Fri, 13 Feb 2009 21:03:08 +0100 Message-ID: <20090213200305.GA5833@nowhere> References: <20090213004812.GA5824@nowhere> <20090213021626.GA5807@nowhere> <20090213030919.GA5826@nowhere> <20090213072601.GA26946@elte.hu> <20090213120451.GA5782@nowhere> <20090213124928.GC5483@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Thomas Gleixner , Thomas Gleixner , LKML , rt-users , Steven Rostedt , Peter Zijlstra , Carsten Emde , Clark Williams To: Ingo Molnar Return-path: Received: from mail-fx0-f20.google.com ([209.85.220.20]:48038 "EHLO mail-fx0-f20.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760AbZBMUDN (ORCPT ); Fri, 13 Feb 2009 15:03:13 -0500 Content-Disposition: inline In-Reply-To: <20090213124928.GC5483@elte.hu> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Fri, Feb 13, 2009 at 01:49:28PM +0100, Ingo Molnar wrote: > > * Frederic Weisbecker wrote: > > > So, just a thing. > > -rt make the hrtimer's timers running on softirq context because the hrtimer_interrupt > > doesn't run as a threaded interrupt, and then it is not preemptible right? > > > > In that case, sysprof will continue to run in hardirq context, as before, and > > it will considerably increase the latency. And that matters here. > > So I think it is important to put it on the reminder: > > hm, not sure. Do you know it numerically how much worst-case overhead it > induces? > > Ingo Not at all. But when I find some time, I will compare some rt average tests with and without sysprof.