Re: [PATCHSET 0/8] perf tools: Do not set attr.exclude_guest by default (v4)

[James Clark <james.clark@linaro.org>]

On 02/10/2024 19:29, Namhyung Kim wrote:
> On Wed, Oct 02, 2024 at 10:49:36AM +0100, James Clark wrote:
>>
>>
>> On 01/10/2024 1:20 am, Namhyung Kim wrote:
>>> Hello,
>>>
>>> I found perf tools set exclude_guest bit inconsistently.  It used to
>>> set the bit but now the default event for perf record doesn't.  So I'm
>>> wondering why we want the bit in the first place.
>>>
>>> Actually it's not good for PMUs don't support any exclusion like AMD
>>> IBS because it disables new features after the exclude_guest due to
>>> the missing feature detection logic.
>>>
>>> v4 changes)
>>>
>>>    * handle EOPNOTSUPP error in compatible way  (Kan)
>>>    * drop --exclude-guest option in perf stat
>>>    * not to separate exclude_hv fallback
>>>    * rename to exclude_GH_default  (Kan)
>>>    * drop the RFC from the subject
>>>
>>> v3) https://lore.kernel.org/lkml/20240905202426.2690105-1-namhyung@kernel.org/
>>>
>>>    * move exclude_guest fallback to the front
>>>    * fix precise_max handling on AMD
>>>    * simplify the default event for perf record
>>>
>>> v2) https://lore.kernel.org/lkml/20240904064131.2377873-1-namhyung@kernel.org/
>>>
>>>    * update the missing feature detection logic
>>>    * separate exclude_hv fallback
>>>    * add new fallback for exclude_guest
>>>
>>> v1) https://lore.kernel.org/lkml/20240902014621.2002343-1-namhyung@kernel.org/
>>>
>>> AFAIK it doesn't matter for the most cases but perf kvm.  If users
>>> need to set the bit, they can still use :H modifier.  For vPMU pass-
>>> through or Apple M1, it'd add the exclude_guest during the fallback
>>> logic.
>>>
>>> Also the kernel feature detection logic should be separated from the
>>> exclude bit tests since it depends on the PMU implementation rather
>>> than the core kernel features.  So I changed it to use a software
>>> event for the detection and factor out some hw-specific checks.
>>>
>>> The code is available at 'perf/exclude-v4' branch in
>>> git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>>>
>>> Thanks,
>>> Namhyung
>>>
>>>
>>
>> Looks like you need to allow for :H in the perf stat test on M1 now:
>>
>> diff --git a/tools/perf/tests/shell/stat.sh b/tools/perf/tests/shell/stat.sh
>> index 5a2ca2bcf94d..77cb95859649 100755
>> --- a/tools/perf/tests/shell/stat.sh
>> +++ b/tools/perf/tests/shell/stat.sh
>> @@ -161,7 +161,7 @@ test_hybrid() {
>>     fi
>>
>>     # Run default Perf stat
>> -  cycles_events=$(perf stat -- true 2>&1 | grep -E "/cycles/|  cycles " |
>> wc -l)
>> +  cycles_events=$(perf stat -- true 2>&1 | grep -E "/cycles/|  cycles |  cycles:H  " | wc -l)
> 
> Ok, what about "u"?  Probably it can be
> 
>    cycles_events=$(perf stat -- true 2>&1 | grep -E "/cycles/(uH)*|  cycles(:[uH])* " | wc -l)
> 

Yep that probably works too and is a bit more robust

>>
>>     if [ "$pmus" -ne "$cycles_events" ]
>>     then
>>
>> Other than that:
>>
>> Reviewed-by: James Clark <james.clark@linaro.org>
> 
> Thanks for the review!
> Namhyung
> 
>>
>>> Namhyung Kim (8):
>>>     perf tools: Add fallback for exclude_guest
>>>     perf tools: Don't set attr.exclude_guest by default
>>>     perf tools: Simplify evsel__add_modifier()
>>>     perf tools: Do not set exclude_guest for precise_ip
>>>     perf tools: Detect missing kernel features properly
>>>     perf tools: Move x86__is_amd_cpu() to util/env.c
>>>     perf tools: Check fallback error and order
>>>     perf record: Just use "cycles:P" as the default event
>>>
>>>    tools/perf/arch/x86/util/Build              |   1 -
>>>    tools/perf/arch/x86/util/env.c              |  19 -
>>>    tools/perf/arch/x86/util/env.h              |   7 -
>>>    tools/perf/arch/x86/util/pmu.c              |   2 +-
>>>    tools/perf/builtin-kvm.c                    |   1 +
>>>    tools/perf/builtin-record.c                 |   4 +-
>>>    tools/perf/builtin-stat.c                   |  18 +-
>>>    tools/perf/dlfilters/dlfilter-test-api-v0.c |   2 +-
>>>    tools/perf/dlfilters/dlfilter-test-api-v2.c |   2 +-
>>>    tools/perf/tests/attr/test-record-dummy-C0  |   2 +-
>>>    tools/perf/tests/parse-events.c             |  30 +-
>>>    tools/perf/util/env.c                       |  24 ++
>>>    tools/perf/util/env.h                       |   4 +
>>>    tools/perf/util/evsel.c                     | 394 ++++++++++++++------
>>>    tools/perf/util/evsel.h                     |   1 -
>>>    tools/perf/util/parse-events.c              |   6 +-
>>>    tools/perf/util/util.c                      |  10 +-
>>>    tools/perf/util/util.h                      |   3 +
>>>    18 files changed, 364 insertions(+), 166 deletions(-)
>>>    delete mode 100644 tools/perf/arch/x86/util/env.c
>>>    delete mode 100644 tools/perf/arch/x86/util/env.h
>>>
>>