linux-kernel - Re: [PATCH 5/5] perf, x86: Support Haswell v4 LBR format v2

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Date:	Tue, 3 Sep 2013 17:14:51 -0400 (EDT)
From:	Vince Weaver <vince@...ter.net>
To:	Andi Kleen <ak@...ux.intel.com>
cc:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] perf, x86: Support Haswell v4 LBR format v2

On Tue, 3 Sep 2013, Andi Kleen wrote:

> > > +	PERF_SAMPLE_BRANCH_ABORT_TX	= 1U << 7, /* transaction aborts */
> > > +	PERF_SAMPLE_BRANCH_IN_TX	= 1U << 8, /* in transaction */
> > > +	PERF_SAMPLE_BRANCH_NO_TX	= 1U << 9, /* not in transaction */
> > 
> > so if you specify these flags in branch_sample_type, what information
> > appears in the branch record?  
> 
> This is just a filter, so when set branches that do not satisfy
> the filter are not reported.

Is the implementation a direct mapping to the LBR documentation or has it 
been generic so non-Intel architectures can use it?

> The patches to export the new fields haven't been merged yet.

What does this mean?  The above values are exported as part of 
  include/uapi/linux/perf_event.h
Do they not work yet?

> >  What happens if you set both in transaction and not in?
> 
> Then you get all branches.

so what happens if you set neither "PERF_SAMPLE_BRANCH_IN_TX" nor
"PERF_SAMPLE_BRANCH_NO_TX"?  Logically you'd get no branches at all,
but that can't be true as all code prior to 3.11 didn't set those values.

Vince
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