To avoid duplicate work in perf_prepare_sample(), save the final header size in data->saved_size. It's initialized to 0 and set to an actual value at the end of perf_prepare_sample(). If it sees a non-zero value that means it's the second time of the call and it knows the sample data is populated already. So update the header size with the data->saved_size and bail out. Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx> --- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 11 +++++++++++ 2 files changed, 13 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index dd565306f479..ccde631a0cb4 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1103,6 +1103,7 @@ struct perf_sample_data { */ u64 sample_flags; u64 period; + u64 saved_size; /* * Fields commonly set by __perf_event_header__init_id(), @@ -1158,6 +1159,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data, /* remaining struct members initialized in perf_prepare_sample() */ data->sample_flags = PERF_SAMPLE_PERIOD; data->period = period; + data->saved_size = 0; if (addr) { data->addr = addr; diff --git a/kernel/events/core.c b/kernel/events/core.c index 70bff8a04583..dac4d76e2877 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7575,6 +7575,15 @@ void perf_prepare_sample(struct perf_event_header *header, header->misc = 0; header->misc |= perf_misc_flags(regs); + /* + * If it called perf_prepare_sample() already, it set the all data fields + * and recorded the final size to data->saved_size. + */ + if (data->saved_size) { + header->size = data->saved_size; + return; + } + /* * Clear the sample flags that have already been done by the * PMU driver. @@ -7796,6 +7805,8 @@ void perf_prepare_sample(struct perf_event_header *header, * do here next. */ WARN_ON_ONCE(header->size & 7); + + data->saved_size = header->size; } static __always_inline int -- 2.39.0.314.g84b9a713c41-goog