Messages in this thread | | | Subject | Re: [PATCH v4 4/7] perf record: Track sideband events for all CPUs when tracing selected CPUs | From | Yang Jihong <> | Date | Fri, 4 Aug 2023 09:42:55 +0800 |
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Hello,
On 2023/8/3 14:28, Adrian Hunter wrote: > On 2/08/23 10:49, Yang Jihong wrote: >> User space tasks can migrate between CPUs, we need to track side-band >> events for all CPUs. >> >> The specific scenarios are as follows: >> >> CPU0 CPU1 >> perf record -C 0 start >> taskA starts to be created and executed >> -> PERF_RECORD_COMM and PERF_RECORD_MMAP >> events only deliver to CPU1 >> ...... >> | >> migrate to CPU0 >> | >> Running on CPU0 <----------/ >> ... >> >> perf record -C 0 stop >> >> Now perf samples the PC of taskA. However, perf does not record the >> PERF_RECORD_COMM and PERF_RECORD_MMAP events of taskA. >> Therefore, the comm and symbols of taskA cannot be parsed. >> >> The solution is to record sideband events for all CPUs when tracing >> selected CPUs. Because this modifies the default behavior, add related >> comments to the perf record man page. >> >> The sys_perf_event_open invoked is as follows: >> >> # perf --debug verbose=3 record -e cpu-clock -C 1 true >> <SNIP> >> Opening: cpu-clock >> ------------------------------------------------------------ >> perf_event_attr: >> type 1 (PERF_TYPE_SOFTWARE) >> size 136 >> config 0 (PERF_COUNT_SW_CPU_CLOCK) >> { sample_period, sample_freq } 4000 >> sample_type IP|TID|TIME|CPU|PERIOD|IDENTIFIER >> read_format ID|LOST >> disabled 1 >> inherit 1 >> freq 1 >> sample_id_all 1 >> exclude_guest 1 >> ------------------------------------------------------------ >> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 5 >> Opening: dummy:u >> ------------------------------------------------------------ >> perf_event_attr: >> type 1 (PERF_TYPE_SOFTWARE) >> size 136 >> config 0x9 (PERF_COUNT_SW_DUMMY) >> { sample_period, sample_freq } 1 >> sample_type IP|TID|TIME|CPU|IDENTIFIER >> read_format ID|LOST >> inherit 1 >> exclude_kernel 1 >> exclude_hv 1 >> mmap 1 >> comm 1 >> task 1 >> sample_id_all 1 >> exclude_guest 1 >> mmap2 1 >> comm_exec 1 >> ksymbol 1 >> bpf_event 1 >> ------------------------------------------------------------ >> sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 6 >> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 7 >> sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 = 9 >> sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 = 10 >> sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 = 11 >> sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 = 12 >> sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 = 13 >> sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 = 14 >> <SNIP> >> >> Signed-off-by: Yang Jihong <yangjihong1@huawei.com> >> --- >> tools/perf/Documentation/perf-record.txt | 3 ++ >> tools/perf/builtin-record.c | 45 +++++++++++++++++++++++- >> 2 files changed, 47 insertions(+), 1 deletion(-) >> >> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt >> index 680396c56bd1..dac53ece51ab 100644 >> --- a/tools/perf/Documentation/perf-record.txt >> +++ b/tools/perf/Documentation/perf-record.txt >> @@ -388,6 +388,9 @@ comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0- >> In per-thread mode with inheritance mode on (default), samples are captured only when >> the thread executes on the designated CPUs. Default is to monitor all CPUs. >> >> +User space tasks can migrate between CPUs, so when tracing selected CPUs, >> +a dummy event is created to track sideband for all CPUs. >> + >> -B:: >> --no-buildid:: >> Do not save the build ids of binaries in the perf.data files. This skips >> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >> index 3ff9d972225e..468afeaac52d 100644 >> --- a/tools/perf/builtin-record.c >> +++ b/tools/perf/builtin-record.c >> @@ -908,10 +908,45 @@ static int record__config_off_cpu(struct record *rec) >> return off_cpu_prepare(rec->evlist, &rec->opts.target, &rec->opts); >> } >> >> +static bool record__tracking_system_wide(struct record *rec) >> +{ >> + struct record_opts *opts = &rec->opts; >> + struct evlist *evlist = rec->evlist; >> + struct evsel *evsel; >> + >> + /* >> + * If all (non-dummy) evsel have exclude_user, >> + * system_wide is not needed. >> + * >> + * all_kernel and all_user will overwrite exclude_kernel and >> + * exclude_user of attr in evsel__config(), here need to check >> + * all the three items. >> + * >> + * Sideband system wide if one of the following conditions is met: >> + * >> + * - all_user is set, and there is a non-dummy event >> + * - all_user and all_kernel are not set, and there is >> + * a non-dummy event without exclude_user >> + */ > > Could start with: > > if (opts->all_kernel) > return false; > >> + evlist__for_each_entry(evlist, evsel) { >> + if (!evsel__is_dummy_event(evsel)) { >> + if (opts->all_user) >> + return true; >> + >> + if (!opts->all_user && !opts->all_kernel && > > !opts->all_user is always true here > >> + !evsel->core.attr.exclude_user) >> + return true; > > So then this could simply be: > > if (opts->all_user || !evsel->core.attr.exclude_user) > return true; > > Thanks for correction. It will be modified in the next version according to the above.
Thanks, Yang
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