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
