Messages in this thread | | | Subject | Re: [PATCH] perf util: Use target->per_thread and target->system_wide flags | From | "Jin, Yao" <> | Date | Tue, 23 Jan 2018 07:02:44 +0800 |
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On 1/23/2018 5:10 AM, Mathieu Poirier wrote: > On 22 January 2018 at 15:15, Jin Yao <yao.jin@linux.intel.com> wrote: >> Mathieu Poirier reports issue in commit ("73c0ca1eee3d perf thread_map: >> Enumerate all threads from /proc") that it has negative impact on >> 'perf record --per-thread'. It has the effect of creating a kernel event >> for each thread in the system for 'perf record --per-thread'. >> >> Mathieu Poirier's patch ("perf util: Do not reuse target->per_thread flag") >> can fix this issue by creating a new target->all_threads flag. >> >> This patch is based on Mathieu Poirier's patch but it doesn't use a new >> target->all_threads flag. This patch just uses 'target->per_thread && >> target->system_wide' as a condition to check for all threads case. >> >> Signed-off-by: Jin Yao <yao.jin@linux.intel.com> >> --- >> tools/perf/util/evlist.c | 2 +- >> tools/perf/util/thread_map.c | 4 ++-- >> tools/perf/util/thread_map.h | 2 +- >> 3 files changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c >> index 120efd8..9dff74a 100644 >> --- a/tools/perf/util/evlist.c >> +++ b/tools/perf/util/evlist.c >> @@ -1106,7 +1106,7 @@ int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target) >> struct thread_map *threads; >> >> threads = thread_map__new_str(target->pid, target->tid, target->uid, >> - target->per_thread); >> + target->per_thread && target->system_wide); > > At first glance I thought your solution would do the trick but perf > record does use target->system_wide when the '-a' switch is used. > Moreover specifying the '-a' switch doesn't prevent the '--per-thread' > option from being used as well, making both target->perf_thread and > target_system_wide equal to true (and that is not good). > > Although not a fan of adding more to struct target, the advantage of > having target->all_threads is that we are guaranteed that it isn't > used anywhere else. > > Let me know what you think, > Mathieu >
If we specify both '-a' and '--per-thread' to perf record, perf record will override'--per-thread'. So now target->per_thread = false, and target->system_wide = true.
If we specify '--per-thread' only to perf record, target->per_thread = true, and target->system_wide = false.
So whatever for any case, target->per_thread && target->system_wide is false.
Since the parameter is false, in thread_map__new_str(), it will not execute the thread_map__new_all_cpus(). So that will not change perf record previous behavior.
In perf stat, it allows the case that target->per_thread and target->system_wide are all true. That means we want to collect system-wide per-thread metrics.
That's my current thinking.
Thanks Jin Yao
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