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

[James Clark]

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@xxxxxxxxxx/
>
>   * 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@xxxxxxxxxx/
>
>   * 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@xxxxxxxxxx/
>
> 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)

   if [ "$pmus" -ne "$cycles_events" ]
   then

Other than that:

Reviewed-by: James Clark <james.clark@xxxxxxxxxx>

> 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