linux-kernel - Re: [PATCH] perf, x86: Optimize intel_pmu_pebs_fixup

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Message-ID: <20131017150944.GQ10651@twins.programming.kicks-ass.net>
Date:	Thu, 17 Oct 2013 17:09:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	dave.hansen@...ux.intel.com, eranian@...gle.com,
	ak@...ux.intel.com, jmario@...hat.com,
	linux-kernel@...r.kernel.org, acme@...radead.org, mingo@...nel.org
Subject: Re: [PATCH] perf, x86: Optimize intel_pmu_pebs_fixup_ip()

On Thu, Oct 17, 2013 at 11:03:58AM -0400, Don Zickus wrote:
> On Thu, Oct 17, 2013 at 04:51:31PM +0200, Peter Zijlstra wrote:
> > On Thu, Oct 17, 2013 at 10:49:13AM -0400, Don Zickus wrote:
> > > For some reason this patch is page faulting at an invalid address inside
> > > __intel_pmu_pebs_event().
> > 
> > Ah yes, I lost a refresh, but read on; I've send a gazillion new emails
> > since ;-)
> 
> Yes, I have noticed, but I got worried when you labeled some of them with
> 'untested'. :-)  Thought I would stick to something a little more close to
> working.
> 
> > 
> > I think it was something like: s/this_cpu_ptr/this_cpu_read/ to make it
> > work again.
> 
> Thanks.  I will try some of the other pieces today (unlike yesterday).

The patches you find in:

http://programming.kicks-ass.net/sekrit/patches.tar.bz2

are actually running on my machine now.

One of the things I was considering was further shrinking the max basic
block size from 4k to maybe 1k or 512 bytes. Not sure what a sane basic
block length limit would be.

I did try 1k earlier today and I seemed to still get near 100% rewind
success rates.

Stephane, Andi, any clues?
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