Messages in this thread | | | Date | Fri, 13 May 2022 13:24:58 -0400 | Subject | Re: [PATCH 1/4] perf evsel: Fixes topdown events in a weak group for the hybrid platform | From | "Liang, Kan" <> |
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On 5/13/2022 12:43 PM, Ian Rogers wrote: > On Fri, May 13, 2022 at 9:24 AM Liang, Kan <kan.liang@linux.intel.com> wrote: >> >> >> >> On 5/13/2022 11:39 AM, Ian Rogers wrote: >>> On Fri, May 13, 2022 at 8:16 AM <kan.liang@linux.intel.com> wrote: >>>> >>>> From: Kan Liang <kan.liang@linux.intel.com> >>>> >>>> The patch ("perf evlist: Keep topdown counters in weak group") fixes the >>>> perf metrics topdown event issue when the topdown events are in a weak >>>> group on a non-hybrid platform. However, it doesn't work for the hybrid >>>> platform. >>>> >>>> $./perf stat -e '{cpu_core/slots/,cpu_core/topdown-bad-spec/, >>>> cpu_core/topdown-be-bound/,cpu_core/topdown-fe-bound/, >>>> cpu_core/topdown-retiring/,cpu_core/branch-instructions/, >>>> cpu_core/branch-misses/,cpu_core/bus-cycles/,cpu_core/cache-misses/, >>>> cpu_core/cache-references/,cpu_core/cpu-cycles/,cpu_core/instructions/, >>>> cpu_core/mem-loads/,cpu_core/mem-stores/,cpu_core/ref-cycles/, >>>> cpu_core/cache-misses/,cpu_core/cache-references/}:W' -a sleep 1 >>>> >>>> Performance counter stats for 'system wide': >>>> >>>> 751,765,068 cpu_core/slots/ (84.07%) >>>> <not supported> cpu_core/topdown-bad-spec/ >>>> <not supported> cpu_core/topdown-be-bound/ >>>> <not supported> cpu_core/topdown-fe-bound/ >>>> <not supported> cpu_core/topdown-retiring/ >>>> 12,398,197 cpu_core/branch-instructions/ (84.07%) >>>> 1,054,218 cpu_core/branch-misses/ (84.24%) >>>> 539,764,637 cpu_core/bus-cycles/ (84.64%) >>>> 14,683 cpu_core/cache-misses/ (84.87%) >>>> 7,277,809 cpu_core/cache-references/ (77.30%) >>>> 222,299,439 cpu_core/cpu-cycles/ (77.28%) >>>> 63,661,714 cpu_core/instructions/ (84.85%) >>>> 0 cpu_core/mem-loads/ (77.29%) >>>> 12,271,725 cpu_core/mem-stores/ (77.30%) >>>> 542,241,102 cpu_core/ref-cycles/ (84.85%) >>>> 8,854 cpu_core/cache-misses/ (76.71%) >>>> 7,179,013 cpu_core/cache-references/ (76.31%) >>>> >>>> 1.003245250 seconds time elapsed >>>> >>>> A hybrid platform has a different PMU name for the core PMUs, while >>>> the current perf hard code the PMU name "cpu". >>>> >>>> The evsel->pmu_name can be used to replace the "cpu" to fix the issue. >>>> For a hybrid platform, the pmu_name must be non-NULL. Because there are >>>> at least two core PMUs. The PMU has to be specified. >>>> For a non-hybrid platform, the pmu_name may be NULL. Because there is >>>> only one core PMU, "cpu". For a NULL pmu_name, we can safely assume that >>>> it is a "cpu" PMU. >>>> >>>> With the patch, >>>> >>>> $perf stat -e '{cpu_core/slots/,cpu_core/topdown-bad-spec/, >>>> cpu_core/topdown-be-bound/,cpu_core/topdown-fe-bound/, >>>> cpu_core/topdown-retiring/,cpu_core/branch-instructions/, >>>> cpu_core/branch-misses/,cpu_core/bus-cycles/,cpu_core/cache-misses/, >>>> cpu_core/cache-references/,cpu_core/cpu-cycles/,cpu_core/instructions/, >>>> cpu_core/mem-loads/,cpu_core/mem-stores/,cpu_core/ref-cycles/, >>>> cpu_core/cache-misses/,cpu_core/cache-references/}:W' -a sleep 1 >>>> >>>> Performance counter stats for 'system wide': >>>> >>>> 766,620,266 cpu_core/slots/ (84.06%) >>>> 73,172,129 cpu_core/topdown-bad-spec/ # 9.5% bad speculation (84.06%) >>>> 193,443,341 cpu_core/topdown-be-bound/ # 25.0% backend bound (84.06%) >>>> 403,940,929 cpu_core/topdown-fe-bound/ # 52.3% frontend bound (84.06%) >>>> 102,070,237 cpu_core/topdown-retiring/ # 13.2% retiring (84.06%) >>>> 12,364,429 cpu_core/branch-instructions/ (84.03%) >>>> 1,080,124 cpu_core/branch-misses/ (84.24%) >>>> 564,120,383 cpu_core/bus-cycles/ (84.65%) >>>> 36,979 cpu_core/cache-misses/ (84.86%) >>>> 7,298,094 cpu_core/cache-references/ (77.30%) >>>> 227,174,372 cpu_core/cpu-cycles/ (77.31%) >>>> 63,886,523 cpu_core/instructions/ (84.87%) >>>> 0 cpu_core/mem-loads/ (77.31%) >>>> 12,208,782 cpu_core/mem-stores/ (77.31%) >>>> 566,409,738 cpu_core/ref-cycles/ (84.87%) >>>> 23,118 cpu_core/cache-misses/ (76.71%) >>>> 7,212,602 cpu_core/cache-references/ (76.29%) >>>> >>>> 1.003228667 seconds time elapsed >>>> >>>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> >>>> --- >>>> tools/perf/arch/x86/util/evsel.c | 5 +++-- >>>> 1 file changed, 3 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c >>>> index 00cb4466b4ca..24510bcb4bf4 100644 >>>> --- a/tools/perf/arch/x86/util/evsel.c >>>> +++ b/tools/perf/arch/x86/util/evsel.c >>>> @@ -33,8 +33,9 @@ void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr) >>>> >>>> bool arch_evsel__must_be_in_group(const struct evsel *evsel) >>>> { >>>> - if ((evsel->pmu_name && strcmp(evsel->pmu_name, "cpu")) || >>>> - !pmu_have_event("cpu", "slots")) >>>> + const char *pmu_name = evsel->pmu_name ? evsel->pmu_name : "cpu"; >>>> + >>>> + if (!pmu_have_event(pmu_name, "slots")) >>> >>> Playing devil's advocate, if I have a PMU for my network accelerator >>> and it has an event called "slots" then this test will also be true. >>> >> >> IIRC, the pmu_have_event should only check the event which is exposed by >> the kernel. It's very unlikely that another PMU expose the exact same name. >> >> If you still worry about it, I think we can check the PMU type >> PERF_TYPE_RAW here, which is reserved for the core PMU. Others cannot >> use it. > > That's cool, this isn't documented behavior though: > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/include/uapi/linux/perf_event.h?h=perf/core#n34 > and PERF_TYPE_HARDWARE wouldn't seem a wholly unreasonable type. It > kind of feels like depending on a quirk, and so we should bury the > quirk in a helper function and document it :-)
The PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE are aliases for the PERF_TYPE_RAW. The PERF_TYPE_HARDWARE is used for the 10 common hardware events and The PERF_TYPE_HW_CACHE is used for the hardware cache events. Other core events (not include the atom core events in a hybrid machine) should have the PERF_TYPE_RAW type.
Since the perf metrics is a big core only feature, checking both the PERF_TYPE_RAW type and the slots event should be good enough here.
I will add more comments in V2.
> >> It looks like arch_evsel__must_be_in_group() is the only user for the >> evsel__sys_has_perf_metrics() for now, so I make it static. >> >> The other pmu_have_event("cpu", "slots") is in evlist.c. >> topdown_sys_has_perf_metrics() in patch 4 should be used to replace it. >> I think Zhengjun will post patches for the changes for the evlist.c > > Ok, is Zhengjun putting his changes on top of this and fixing up the > APIs or is he waiting on these changes landing? Let me know how to > help. I'm guessing landing my changes is the first step.
Right. Your changes is the first step. Then this patch set. Zhengjun's will be on top of us.
Thanks, Kan
> > Thanks, > Ian > >> diff --git a/tools/perf/arch/x86/util/evsel.c >> b/tools/perf/arch/x86/util/evsel.c >> index 24510bcb4bf4..a4714174e30f 100644 >> --- a/tools/perf/arch/x86/util/evsel.c >> +++ b/tools/perf/arch/x86/util/evsel.c >> @@ -31,11 +31,20 @@ void arch_evsel__fixup_new_cycles(struct >> perf_event_attr *attr) >> free(env.cpuid); >> } >> >> -bool arch_evsel__must_be_in_group(const struct evsel *evsel) >> +static bool evsel__sys_has_perf_metrics(const struct evsel *evsel) >> { >> const char *pmu_name = evsel->pmu_name ? evsel->pmu_name : "cpu"; >> >> - if (!pmu_have_event(pmu_name, "slots")) >> + if ((evsel->core.attr.type == PERF_TYPE_RAW) && >> + pmu_have_event(pmu_name, "slots")) >> + return true; >> + >> + return false; >> +} >> + >> +bool arch_evsel__must_be_in_group(const struct evsel *evsel) >> +{ >> + if (!evsel__sys_has_perf_metrics(evsel)) >> return false; >> >> return evsel->name && >> >> Thanks, >> Kan >> >>> The property that is being tested here is "does this CPU have topdown >>> events" and so allowing any PMU removes the "does this CPU" part of >>> the equation. I think ideally we'd have an arch functions something >>> like: >>> >>> bool arch_pmu__has_intel_topdown_events(void) >>> { >>> static bool has_topdown_events = pmu_have_event("cpu", "slots") || >>> pmu_have_event("cpu_core", "slots"); >>> >>> return has_topdown_events; >>> } >>> >>> bool arch_pmu__supports_intel_topdown_events(const char *pmu_name) >>> { >>> if (!pmu_name) >>> return false; >>> return arch_pmu__has_intel_topdown_events() && (!strncmp(pmu_name, >>> "cpu") || !strncmp(pmu_name, "cpu_core")); >>> } >>> >>> bool arch_evsel__is_intel_topdown_event(struct evsel *evsel) >>> { >>> if (!arch_pmu__supports_intel_topdown_events(evsel->pmu)) >>> return false; >>> >>> return strcasestr(evsel->name, "slots") || strcasestr(evsel->name, "topdown"); >>> } >>> >>> This then gives us: >>> >>> bool arch_evsel__must_be_in_group(const struct evsel *evsel) >>> { >>> return arch_evsel__is_intel_topdown_event(evsel); >>> } >>> >>> These functions can then be reused for the arch_evlist topdown code, >>> etc. What I don't see in these functions is use of any hybrid >>> abstraction and so it isn't clear to me how with hybrid something like >>> this would be plumbed in. >>> >>> Thanks, >>> Ian >>> >>>> return false; >>>> >>>> return evsel->name && >>>> -- >>>> 2.35.1 >>>>
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