linux-kernel - Re: [patch 0/2] NOHZ vs. profile/oprofile v2

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Date:	Wed, 24 Jun 2009 19:47:34 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Robert Richter <robert.richter@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Rob van der Heij <rvdheij@...il.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	john stultz <johnstul@...ibm.com>,
	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [patch 0/2] NOHZ vs. profile/oprofile v2


* Martin Schwidefsky <schwidefsky@...ibm.com> wrote:

> On Mon, 22 Jun 2009 17:40:30 +0200
> Ingo Molnar <mingo@...e.hu> wrote:
> 
> > 
> > * Martin Schwidefsky <schwidefsky@...ibm.com> wrote:
> > 
> > > On Mon, 22 Jun 2009 17:29:37 +0200
> > > Ingo Molnar <mingo@...e.hu> wrote:
> > > 
> > > > 
> > > > * Martin Schwidefsky <schwidefsky@...ibm.com> wrote:
> > > > 
> > > > > [...] And if we really want to keep things separate there will be 
> > > > > two sets of per-cpu hrtimer, one for the old style profiler and 
> > > > > one for oprofile. Any preference for the user space interface to 
> > > > > set the sample rate? A sysctl?
> > > > 
> > > > I dont think we want to keep things separate. Regarding old-style 
> > > > profiler, does anyone still use it? There's now a superior in-tree 
> > > > replacement for it, so we could phase it out.
> > > 
> > > Well, for my part I won't miss it. But to be able to remove the 
> > > profile_tick() calls from the architectures I either have to rip 
> > > out the old profiler now, or adapt it to use hrtimer as well.
> > 
> > Do we _have to_ touch it so widely right now? We could start with a 
> > deprecation warning in this cycle. Once it's deprecated we can 
> > remove all those calls.
> 
> First version of the hrtimer patch for oprofile. I did not add the 
> sysctl yet, if the sysctl is added in oprofile_timer_init it would 
> not be available if some better profiling source is available. If 
> it is added unconditionally it would only have an effect if the 
> timer fallback is used. Both cases are not exactly nice for a user 
> space interface.

looks quite sane. I've Cc:-ed Robert.

	Ingo
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