2022-12-29 20:53:25

by Namhyung Kim

Subject: [PATCH 3/3] perf/core: Save calculated sample data size

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 <[email protected]>
---
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

2023-01-09 17:05:24

by tip-bot2 for Alexey Makhalov

Subject: [tip: perf/core] perf/core: Save calculated sample data size

The following commit has been merged into the perf/core branch of tip:

Commit-ID: 0ecc518e5c1a83fbfc6262d20d0df289eafc2207
Gitweb: https://git.kernel.org/tip/0ecc518e5c1a83fbfc6262d20d0df289eafc2207
Author: Namhyung Kim <[email protected]>
AuthorDate: Thu, 29 Dec 2022 12:41:01 -08:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Mon, 09 Jan 2023 12:22:09 +01:00

perf/core: Save calculated sample data size

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 <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
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 03949d0..656b6ea 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 70bff8a..dac4d76 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7576,6 +7576,15 @@ void perf_prepare_sample(struct perf_event_header *header,
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