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Date: Fri, 6 May 2022 12:27:17 +0300 From: Adrian Hunter <adrian.hunter@...el.com> To: Ian Rogers <irogers@...gle.com> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...hat.com>, Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, Leo Yan <leo.yan@...aro.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH V1 13/23] perf evlist: Add evlist__add_system_wide_dummy() On 6/05/22 11:34, Ian Rogers wrote: > On Fri, May 6, 2022 at 1:14 AM Adrian Hunter <adrian.hunter@...el.com> wrote: >> >> On 6/05/22 02:56, Ian Rogers wrote: >>> On Thu, May 5, 2022 at 9:57 AM Adrian Hunter <adrian.hunter@...el.com> wrote: >>>> >>>> Add evlist__add_system_wide_dummy() to enable creating a system-wide dummy >>>> event that sets up the system-wide maps before map propagation. >>> >>> Perhaps this should be: >>> evlist__add_dummy_on_all_online_cpus() >> >> Ok, but offline isn't an option, so I'll drop 'online' from the name. > > I'm not sure I follow. There can be CPUs that are offline (echo 0 > > /sys/devices/system/cpu/cpu2/online) and then brought online while > perf is running. The output obviously won't be right as we're missing > dummy events. Losing online from the name here seems to remove a > useful clue. perf_event_open() will not accept events on offline CPUs. > > Thanks, > Ian > >>> my thoughts being that a system wide dummy sounds like the dummy CPU >>> map, ie {-1} whilst what happens here is opening on all online CPUs >>> {0-35} on a 36 hyperthread system. Note also that the libperf >>> cpu_map__read_all_cpu_map code doesn't discover sysfs' mount properly, >>> as done in: >>> tools/lib/api/fs/fs.h >>> Some tech debt. >>> >>>> For convenience, add evlist__add_aux_dummy() so that the logic can be used >>>> whether or not the event needs to be system-wide. >>>> >>>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com> >>>> --- >>>> tools/perf/util/evlist.c | 40 ++++++++++++++++++++++++++++++++++++++++ >>>> tools/perf/util/evlist.h | 5 +++++ >>>> 2 files changed, 45 insertions(+) >>>> >>>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c >>>> index 78c47cbafbc2..58ea562ddbd2 100644 >>>> --- a/tools/perf/util/evlist.c >>>> +++ b/tools/perf/util/evlist.c >>>> @@ -264,6 +264,46 @@ int evlist__add_dummy(struct evlist *evlist) >>>> return 0; >>>> } >>>> >>>> +static void evlist__add_system_wide(struct evlist *evlist, struct evsel *evsel) >>> >>> This would be: >>> evlist__add_on_all_online_cpus(..) >>> >>>> +{ >>>> + evsel->core.system_wide = true; >>>> + >>>> + /* All CPUs */ >>>> + perf_cpu_map__put(evsel->core.own_cpus); >>>> + evsel->core.own_cpus = perf_cpu_map__new(NULL); >>>> + perf_cpu_map__put(evsel->core.cpus); >>>> + evsel->core.cpus = perf_cpu_map__get(evsel->core.own_cpus); >>>> + >>>> + /* No threads */ >>>> + perf_thread_map__put(evsel->core.threads); >>>> + evsel->core.threads = perf_thread_map__new_dummy(); >>>> + >>>> + evlist__add(evlist, evsel); >>>> +} >>>> + >>>> +struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide) >>>> +{ >>>> + struct evsel *evsel = evlist__dummy_event(evlist); >>>> + >>>> + if (!evsel) >>>> + return NULL; >>>> + >>>> + evsel->core.attr.exclude_kernel = 1; >>>> + evsel->core.attr.exclude_guest = 1; >>>> + evsel->core.attr.exclude_hv = 1; >>>> + evsel->core.attr.freq = 0; >>>> + evsel->core.attr.sample_period = 1; >>>> + evsel->no_aux_samples = true; >>>> + evsel->name = strdup("dummy:u"); >>>> + >>>> + if (system_wide) >>>> + evlist__add_system_wide(evlist, evsel); >>>> + else >>>> + evlist__add(evlist, evsel); >>>> + >>>> + return evsel; >>>> +} >>>> + >>>> static int evlist__add_attrs(struct evlist *evlist, struct perf_event_attr *attrs, size_t nr_attrs) >>>> { >>>> struct evsel *evsel, *n; >>>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h >>>> index 4062f5aebfc1..dd1af114e033 100644 >>>> --- a/tools/perf/util/evlist.h >>>> +++ b/tools/perf/util/evlist.h >>>> @@ -114,6 +114,11 @@ int arch_evlist__add_default_attrs(struct evlist *evlist); >>>> struct evsel *arch_evlist__leader(struct list_head *list); >>>> >>>> int evlist__add_dummy(struct evlist *evlist); >>>> +struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide); >>>> +static inline struct evsel *evlist__add_system_wide_dummy(struct evlist *evlist) >>>> +{ >>>> + return evlist__add_aux_dummy(evlist, true); >>>> +} >>>> >>>> int evlist__add_sb_event(struct evlist *evlist, struct perf_event_attr *attr, >>>> evsel__sb_cb_t cb, void *data); >>>> -- >>>> 2.25.1 >>>> >>
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