Messages in this thread | | | Subject | Re: [PATCH] perf/tests: Fix test case 95 on s390 and use same event | From | German Gomez <> | Date | Thu, 28 Jul 2022 10:25:17 +0100 |
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Thanks for the fix, Thomas
On 27/07/2022 15:14, Thomas Richter wrote: > On linux-next tree perf test 95 was added recently. > s390 does not support branch sampling at all and the test case fails > despite for checking branch support before hand. > The check for support of branching > uses the software event named dummy, as seen in the line: > > perf record -b -o- -e dummy -B true > /dev/null 2>&1 || exit 2
Just curious, do you know why the command succeeds in this platform (and potentially others)?
I got the idea of using "dummy" from [1] but only tested on arm64 and x86. I thought the platforms would reject it if -b was not implemented regardless of the event. Did I misunderstand the use of dummy?
Thanks, German
[1] https://lore.kernel.org/all/20220617073840.GA45710@leoy-ThinkPad-X240s/
> > However when the branch recording is actually done, a different > event is used, as seen in the line: > > perf record -o $TMPDIR/... --branch-filter any,save_type,u -- ... > > The event is omitted and for perf record the default event is > cycles, which is not supported by s390 and this fails when executed > on s390: > > # perf record --branch-filter any,save_type,u -- \ > /tmp/__perf_test.program.iDSmQ/a.out > Error: > cycles: PMU Hardware or event type doesn't support branch stack sampling. > # > > Therefore fix this and use the same event cycles for testing support > and actually running the test. > > Output before: > # ./perf test -Fv 95 > 95: Check branch stack sampling : > --- start --- > Testing user branch stack sampling > ---- end ---- > Check branch stack sampling: FAILED! > # > > Output after: > # ./perf test -Fv 95 > 95: Check branch stack sampling : > --- start --- > ---- end ---- > Check branch stack sampling: Skip > # > > Fixes: b55878c90ab9 ("perf test: Add test for branch stack sampling") > Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> > --- > tools/perf/tests/shell/test_brstack.sh | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/tests/shell/test_brstack.sh b/tools/perf/tests/shell/test_brstack.sh > index 113ccd17bf03..c644f94a6500 100755 > --- a/tools/perf/tests/shell/test_brstack.sh > +++ b/tools/perf/tests/shell/test_brstack.sh > @@ -12,7 +12,7 @@ if ! [ -x "$(command -v cc)" ]; then > fi > > # skip the test if the hardware doesn't support branch stack sampling > -perf record -b -o- -e dummy -B true > /dev/null 2>&1 || exit 2 > +perf record -b -o- -B true > /dev/null 2>&1 || exit 2 > > TMPDIR=$(mktemp -d /tmp/__perf_test.program.XXXXX) >
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