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

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Date:	Tue, 10 Sep 2013 09:22:51 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Michael Ellerman <michael@...erman.id.au>
CC:	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	eranian@...gle.com, acme@...hat.com,
	Michael Neuling <michael.neuling@....ibm.com>,
	svaidy@...ux.vnet.ibm.com, sukadev@...ux.vnet.ibm.com
Subject: Re: [PATCH V2 0/6] perf: New conditional branch filter

On 09/10/2013 07:36 AM, Michael Ellerman 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?

I believe it does match. X86 code drops the branch records (originally captured
in the LBR) while applying the SW filters.

Regards
Anshuman

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