From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932287Ab0IGReh (ORCPT <rfc822;w@1wt.eu>);
	Tue, 7 Sep 2010 13:34:37 -0400
Received: from www.tglx.de ([62.245.132.106]:46011 "EHLO www.tglx.de"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1757027Ab0IGRef (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Tue, 7 Sep 2010 13:34:35 -0400
Date: Tue, 7 Sep 2010 19:33:53 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
cc: paulus <paulus@samba.org>, stephane eranian <eranian@googlemail.com>,
        Robert Richter <robert.richter@amd.com>,
        Will Deacon <will.deacon@arm.com>, Paul Mundt <lethal@linux-sh.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>, Lin Ming <ming.m.lin@intel.com>,
        Yanmin <yanmin_zhang@linux.intel.com>,
        Deng-Cheng Zhu <dengcheng.zhu@gmail.com>,
        David Miller <davem@davemloft.net>, Ingo Molnar <mingo@elte.hu>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 13/19] perf: Per cpu-context rotation timer
In-Reply-To: <1283879247.1930.1629.camel@laptop>
Message-ID: <alpine.LFD.2.00.1009071932540.2477@localhost6.localdomain6>
References: <20100907164633.879932949@chello.nl>  <20100907165011.939993481@chello.nl> <1283879247.1930.1629.camel@laptop>
User-Agent: Alpine 2.00 (LFD 1167 2008-08-23)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 7 Sep 2010, Peter Zijlstra wrote:

> On Tue, 2010-09-07 at 18:46 +0200, Peter Zijlstra wrote:
> 
> > @@ -5904,6 +5930,9 @@ static void __init perf_event_init_all_c
> >  
> >                 cpuctx = &per_cpu(perf_cpu_context, cpu);
> >                 __perf_event_init_context(&cpuctx->ctx, NULL);
> > +               cpuctx->timer_interval = TICK_NSEC;
> > +               hrtimer_init(&cpuctx->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > +               cpuctx->timer.function = perf_event_context_tick;
> >         }
> 
> > +static void perf_pmu_rotate_start(struct pmu *pmu)
> > +{
> > +       struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
> > +
> > +       if (hrtimer_active(&cpuctx->timer))
> > +               return;
> > +
> > +       __hrtimer_start_range_ns(&cpuctx->timer,
> > +                       ns_to_ktime(cpuctx->timer_interval), 0,
> > +                       HRTIMER_MODE_REL, 0);
> >  } 
> 
> This probably wants a fuzz factor that lets it fold into the tick we
> already have. Thomas what's the easiest way to do that, give it a soft
> limit of 1ns and hardlimit of TICK_NSEC?

Hmm, why don't you hang it off the tick right away ?

Thanks,

	tglx