linux-kernel - Re: [PATCH 0/7] perf updates and fixes

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Date:	Fri, 26 Mar 2010 18:38:44 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Paul Mackerras <paulus@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Miller <davem@...emloft.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Archs <linux-arch@...r.kernel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 0/7] perf updates and fixes

On Fri, Mar 26, 2010 at 08:58:17AM +0100, Ingo Molnar wrote:
> 
> * Paul Mackerras <paulus@...ba.org> wrote:
> 
> > On Fri, Mar 26, 2010 at 02:52:35AM +0100, Frederic Weisbecker wrote:
> > 
> > > The series is not yet mergeable because it would break PowerPc (hot regs 
> > > snapshot API has been changed, and I don't know how to update PowerPc for 
> > > that).
> > > 
> > > But if you're fine with the ideas, I can integrate the necessary changes 
> > > to fix this, and also separate fixes and updates.
> > 
> > The patch below adds the necessary stuff for powerpc.  You could fold it 
> > into your "perf: Move perf_arch_fetch_caller_regs into a macro" patch, or 
> > keep it as a separate patch in the series (though that would make preserving 
> > bisectability more difficult).
> 
> Since the series needs a resend anyway folding back ought to be fine i think.
> 
> I'm wondering whether this should get into tip:perf/urgent - or in 
> tip:perf/core for 2.6.35.
> 
> It fixes sw event call trace ugliness, but is that a 2.6.34 regression? Is 
> there any other aspect of the series that points towards accelerating this 
> into .34?


Let's have a look:

	perf: Correctly align perf event tracing buffer

Should probably go into urgent. The change is not invasive at
all. It doesn't fix a regression but it's still an important fix.

	The rest

It depends. The whole bunch is rather invasive.
The callchains of context switches never worked correctly
I think. I couldn't tell if the cpu migration has ever worked.
If it ever did, then it's a regression fix but in the middle of
too much hot regs improvements. So I can cook a specific fix for
the cpu migration event to work, and keep the rest for perf/core.

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