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:

quoted

	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.

...

quoted

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