linux-kernel - Re: [PATCH V2 0/6] perf: New conditional branch filter

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Message-ID: <CABPqkBREXH5VUkULAsWvmpCer-s4SCxuof6LdqRO0i-iBOG8pA@mail.gmail.com>
Date:	Sat, 21 Sep 2013 08:55:37 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PPC dev <linuxppc-dev@...abs.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Michael Neuling <michael.neuling@....ibm.com>,
	svaidy@...ux.vnet.ibm.com,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Subject: Re: [PATCH V2 0/6] perf: New conditional branch filter

On Tue, Sep 10, 2013 at 4:06 AM, Michael Ellerman
<michael@...erman.id.au> wrote:
>
> On Fri, 2013-08-30 at 09:54 +0530, Anshuman Khandual wrote:
> >       This patchset is the re-spin of the original branch stack sampling
> > patchset which introduced new PERF_SAMPLE_BRANCH_COND filter. This patchset
> > also enables SW based branch filtering support for PPC64 platforms which have
> > branch stack sampling support. With this new enablement, the branch filter support
> > for PPC64 platforms have been extended to include all these combinations discussed
> > below with a sample test application program.
>
> ...
>
> > Mixed filters
> > -------------
> > (6) perf record -e branch-misses:u -j any_call,any_ret ./cprog
> > Error:
> > The perf.data file has no samples!
> >
> > NOTE: As expected. The HW filters all the branches which are calls and SW tries to find return
> > branches in that given set. Both the filters are mutually exclussive, so obviously no samples
> > found in the end profile.
>
> The semantics of multiple filters is not clear to me. It could be an OR,
> or an AND. You have implemented AND, does that match existing behaviour
> on x86 for example?
>
The semantic on the API is OR. AND does not make sense: CALL & RETURN?
On x86, the HW filter is an OR (default: ALL, set bit to disable a
type). I suspect
it is similar on PPC.

>
> cheers
>
>
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