Messages in this thread | | | Date | Wed, 16 Mar 2022 16:37:06 +0530 | Subject | Re: [PATCH v6 10/12] perf tools: Improve IBS error handling | From | Ravi Bangoria <> |
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Stephane,
On 16-Mar-22 5:33 AM, Stephane Eranian wrote: > On Tue, Mar 15, 2022 at 12:46 AM Ravi Bangoria <ravi.bangoria@amd.com> wrote: >> >> Stephane, >> >> On 09-Feb-22 2:46 AM, Stephane Eranian wrote: >>> From: Kim Phillips <kim.phillips@amd.com> >>> >>> improve the error message returned on failed perf_event_open() on AMD when >>> using IBS. >>> >>> Output of executing 'perf record -e ibs_op// true' BEFORE this patch: >>> >>> The sys_perf_event_open() syscall returned with 22 (Invalid argument)for event (ibs_op//u). >>> /bin/dmesg | grep -i perf may provide additional information. >>> >>> Output after: >>> >>> AMD IBS cannot exclude kernel events. Try running at a higher privilege level. >>> >>> Output of executing 'sudo perf record -e ibs_op// true' BEFORE this patch: >>> >>> Error: >>> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (ibs_op//). >>> /bin/dmesg | grep -i perf may provide additional information. >>> >>> Output after: >>> >>> Error: >>> AMD IBS may only be available in system-wide/per-cpu mode. Try using -a, or -C and workload affinity >> >> This patch seems to be causing regression to perf python test. >> >> Without this patch: >> >> $ sudo ./perf test -vvv 19 >> 19: 'import perf' in python : >> --- start --- >> test child forked, pid 145391 >> python usage test: "echo "import sys ; sys.path.append('python'); import perf" | '/usr/bin/python2' " >> test child finished with 0 >> ---- end ---- >> 'import perf' in python: Ok >> >> With this patch: >> >> $ sudo ./perf test -vvv 19 >> 19: 'import perf' in python : >> --- start --- >> test child forked, pid 144415 >> python usage test: "echo "import sys ; sys.path.append('python'); import perf" | '/usr/bin/python2' " >> Traceback (most recent call last): >> File "<stdin>", line 1, in <module> >> ImportError: python/perf.so: undefined symbol: perf_env__cpuid >> test child finished with -1 >> ---- end ---- >> 'import perf' in python: FAILED! >> > > The fix I sent you is just to prevent a potential SEGFAULT in > is_amd_ibs(). I bet the test fails some perf_event_open() > and ends up in strerror function and from there I don't see how the > patch could impact the test, given you'd segfault > otherwise. > > I tried on my side and with or without this patch this test fails. I > think this looks like an unrelated issue.
That's strange. IIUC, python/perf.so needs to know about util/evsel.c which can be done by adding an entry in util/python-ext-sources.
In any case, do we really need this patch now? For both the example given in description, I see no difference with or without patch:
Without patch:
$ sudo ./perf record -e ibs_op// true Error: Invalid event (ibs_op//) in per-thread mode, enable system wide with '-a'.
$ ./perf record -e ibs_op// true Error: Invalid event (ibs_op//u) in per-thread mode, enable system wide with '-a'.
Same o/p with the patch as well.
Thanks, Ravi
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