[RESEND PATCH 09/12] perf: Extend perf_output_read

kan.liang
2024-06-18T15:12:21Z

From: Kan Liang <kan.liang@linux.intel.com>

The event may have been updated in the PMU-specific implementation,
e.g., Intel PEBS counters snapshotting. The common code should not
read and overwrite the value.

The PERF_SAMPLE_READ in the data->sample_type can be used to detect
whether the PMU-specific value is available. If yes, avoid the
pmu->read() in the common code.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
kernel/events/core.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8f908f077935..733e507948e6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7243,7 +7243,7 @@ static void perf_output_read_one(struct perf_output_handle *handle,

static void perf_output_read_group(struct perf_output_handle *handle,
struct perf_event *event,
- u64 enabled, u64 running)
+ u64 enabled, u64 running, bool read)
{
struct perf_event *leader = event->group_leader, *sub;
u64 read_format = event->attr.read_format;
@@ -7265,7 +7265,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
values[n++] = running;

- if ((leader != event) &&
+ if ((leader != event) && read &&
(leader->state == PERF_EVENT_STATE_ACTIVE))
leader->pmu->read(leader);

@@ -7280,7 +7280,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
for_each_sibling_event(sub, leader) {
n = 0;

- if ((sub != event) &&
+ if ((sub != event) && read &&
(sub->state == PERF_EVENT_STATE_ACTIVE))
sub->pmu->read(sub);

@@ -7307,7 +7307,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
* on another CPU, from interrupt/NMI context.
*/
static void perf_output_read(struct perf_output_handle *handle,
- struct perf_event *event)
+ struct perf_event *event,
+ bool read)
{
u64 enabled = 0, running = 0, now;
u64 read_format = event->attr.read_format;
@@ -7325,7 +7326,7 @@ static void perf_output_read(struct perf_output_handle *handle,
calc_timer_values(event, &now, &enabled, &running);

if (event->attr.read_format & PERF_FORMAT_GROUP)
- perf_output_read_group(handle, event, enabled, running);
+ perf_output_read_group(handle, event, enabled, running, read);
else
perf_output_read_one(handle, event, enabled, running);
}
@@ -7367,7 +7368,7 @@ void perf_output_sample(struct perf_output_handle *handle,
perf_output_put(handle, data->period);

if (sample_type & PERF_SAMPLE_READ)
- perf_output_read(handle, event);
+ perf_output_read(handle, event, !(data->sample_flags & PERF_SAMPLE_READ));

if (sample_type & PERF_SAMPLE_CALLCHAIN) {
int size = 1;
@@ -7968,7 +7969,7 @@ perf_event_read_event(struct perf_event *event,
return;

perf_output_put(&handle, read_event);
- perf_output_read(&handle, event);
+ perf_output_read(&handle, event, true);
perf_event__output_id_sample(event, &handle, &sample);

perf_output_end(&handle);
--
2.35.1