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

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Date:	Wed, 4 Sep 2013 10:05:01 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Vince Weaver <vince@...ter.net>
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 Wed, Sep 04, 2013 at 10:21:27AM -0400, Vince Weaver wrote:
> On Wed, 4 Sep 2013, Andi Kleen wrote:
> 
> > > What does this mean?  The above values are exported as part of 
> > >   include/uapi/linux/perf_event.h
> > > Do they not work yet?
> > 
> > You can filter on the fields, but you can't see them outside
> > the kernel driver yet.  The patch to see them is still pending.
> 
> so you can filter for aborts, but they'll never show up in the lbr[]
> sample buffer?

They will show up, you just don't know that they are aborts 
because the two new status bits are not exported.

> 
> > > > >  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.
> > 
> > Then you get all branches too
> > 
> > (that's how all the other filters work too)
> 
> This is a really confusing API
> 
> so does setting "PERF_SAMPLE_BRANCH_ANY" also enable all of the TX types?
> 
> Is leaving branch_sample_type at 0 the same as setting it to all 1s?

I believe so.

It may be also that the catch all only works if everything is 0.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only
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