From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932324Ab0HaOyJ (ORCPT ); Tue, 31 Aug 2010 10:54:09 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:63881 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757512Ab0HaOyH (ORCPT ); Tue, 31 Aug 2010 10:54:07 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=C9VMPVAWboOArHyGPnU85Fxvmh9V5ILHzm3kabzu1V2sB7k0PRyHJTlJHAEgtY6THX fBLIFmZcxEbfo+NuDvc3q0Xb3jHpimWYYhaSVEQiHnOmLuToTrHBDX85lVK97KYQ551H xxoo5UXmfNlG3j8zN+dQgPsOfo160oCyjbZHA= Date: Tue, 31 Aug 2010 16:54:07 +0200 From: Frederic Weisbecker To: Matt Fleming Cc: Peter Zijlstra , Zhang Rui , linux-kernel@vger.kernel.org, Ingo Molnar , Robert Richter , Lin Ming , Paul Mackerras , Arnaldo Carvalho de Melo , Don Zickus , Cyrill Gorcunov , Len Brown , Matthew Garrett Subject: Re: [RFC][PATCH 1/5] perf: Check if we should exclude idle thread in perf_exclude_event() Message-ID: <20100831145405.GB5259@nowhere> References: <72c0ed93ff0b24365cc4d0a40e24efa3be3fe3df.1283123521.git.matt@console-pimps.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <72c0ed93ff0b24365cc4d0a40e24efa3be3fe3df.1283123521.git.matt@console-pimps.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 30, 2010 at 01:13:43PM +0100, Matt Fleming wrote: > Don't open code the event check for excluding the idle thread. Instead > include the check in perf_exclude_event(). > > Signed-off-by: Matt Fleming > --- > kernel/perf_event.c | 8 +++++--- > 1 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/kernel/perf_event.c b/kernel/perf_event.c > index 0d38f27..16b0476 100644 > --- a/kernel/perf_event.c > +++ b/kernel/perf_event.c > @@ -4310,6 +4310,9 @@ static int perf_exclude_event(struct perf_event *event, > > if (event->attr.exclude_kernel && !user_mode(regs)) > return 1; > + > + if (event->attr.exclude_idle && current->pid == 0) > + return 1; Right. But one of the problems people have reported is that they can miss interrupts samples if they happen in idle. Hence we have decided that exclude_idle should exclude events that happen in idle process context but not in interrupts interrupting idle. So adding an in_interrupt() check would perhaps be better. I plan to do this exclusion using the per context exclusion, which is a patchset I have in queue. But until then, having this patch is better. > } > > return 0; > @@ -4512,9 +4515,8 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer) > regs = get_irq_regs(); > > if (regs && !perf_exclude_event(event, regs)) { > - if (!(event->attr.exclude_idle && current->pid == 0)) > - if (perf_event_overflow(event, 0, &data, regs)) > - ret = HRTIMER_NORESTART; > + if (perf_event_overflow(event, 0, &data, regs)) > + ret = HRTIMER_NORESTART; But yeah if we add an in_interrupt() check in perf_exclude_event(), it won't work here. This one needs to check if irqs are nesting :) Bah, checking we interrupted softirqs is probably enough. I guess we don't care about nesting hardirqs.