This is a note to let you know that I've just added the patch titled
perf/core: Add a new read format to get a number of lost samples
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-core-add-a-new-read-format-to-get-a-number-of-l.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6ae9186f2ee8a48d2233ed733508292406a9a0b3
Author: Namhyung Kim <namhyung@xxxxxxxxxx>
Date: Thu Jun 16 11:06:23 2022 -0700
perf/core: Add a new read format to get a number of lost samples
[ Upstream commit 119a784c81270eb88e573174ed2209225d646656 ]
Sometimes we want to know an accurate number of samples even if it's
lost. Currenlty PERF_RECORD_LOST is generated for a ring-buffer which
might be shared with other events. So it's hard to know per-event
lost count.
Add event->lost_samples field and PERF_FORMAT_LOST to retrieve it from
userspace.
Original-patch-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220616180623.1358843-1-namhyung@xxxxxxxxxx
Stable-dep-of: 382c27f4ed28 ("perf: Fix perf_event_validate_size()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d46eeddeb8593..123e4d715c98d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -685,6 +685,8 @@ struct perf_event {
struct pid_namespace *ns;
u64 id;
+ atomic64_t lost_samples;
+
u64 (*clock)(void);
perf_overflow_handler_t overflow_handler;
void *overflow_handler_context;
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 5fb4cdf37100c..140024b2db381 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -273,6 +273,7 @@ enum {
* { u64 time_enabled; } && PERF_FORMAT_TOTAL_TIME_ENABLED
* { u64 time_running; } && PERF_FORMAT_TOTAL_TIME_RUNNING
* { u64 id; } && PERF_FORMAT_ID
+ * { u64 lost; } && PERF_FORMAT_LOST
* } && !PERF_FORMAT_GROUP
*
* { u64 nr;
@@ -280,6 +281,7 @@ enum {
* { u64 time_running; } && PERF_FORMAT_TOTAL_TIME_RUNNING
* { u64 value;
* { u64 id; } && PERF_FORMAT_ID
+ * { u64 lost; } && PERF_FORMAT_LOST
* } cntr[nr];
* } && PERF_FORMAT_GROUP
* };
@@ -289,8 +291,9 @@ enum perf_event_read_format {
PERF_FORMAT_TOTAL_TIME_RUNNING = 1U << 1,
PERF_FORMAT_ID = 1U << 2,
PERF_FORMAT_GROUP = 1U << 3,
+ PERF_FORMAT_LOST = 1U << 4,
- PERF_FORMAT_MAX = 1U << 4, /* non-ABI */
+ PERF_FORMAT_MAX = 1U << 5, /* non-ABI */
};
#define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3c8eb5d842142..acc6403fc87be 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1725,6 +1725,9 @@ static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
if (event->attr.read_format & PERF_FORMAT_ID)
entry += sizeof(u64);
+ if (event->attr.read_format & PERF_FORMAT_LOST)
+ entry += sizeof(u64);
+
if (event->attr.read_format & PERF_FORMAT_GROUP) {
nr += nr_siblings;
size += sizeof(u64);
@@ -4816,11 +4819,15 @@ static int __perf_read_group_add(struct perf_event *leader,
values[n++] += perf_event_count(leader);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&leader->lost_samples);
for_each_sibling_event(sub, leader) {
values[n++] += perf_event_count(sub);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&sub->lost_samples);
}
unlock:
@@ -4874,7 +4881,7 @@ static int perf_read_one(struct perf_event *event,
u64 read_format, char __user *buf)
{
u64 enabled, running;
- u64 values[4];
+ u64 values[5];
int n = 0;
values[n++] = __perf_event_read_value(event, &enabled, &running);
@@ -4884,6 +4891,8 @@ static int perf_read_one(struct perf_event *event,
values[n++] = running;
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(event);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&event->lost_samples);
if (copy_to_user(buf, values, n * sizeof(u64)))
return -EFAULT;
@@ -6193,7 +6202,7 @@ static void perf_output_read_one(struct perf_output_handle *handle,
u64 enabled, u64 running)
{
u64 read_format = event->attr.read_format;
- u64 values[4];
+ u64 values[5];
int n = 0;
values[n++] = perf_event_count(event);
@@ -6207,6 +6216,8 @@ static void perf_output_read_one(struct perf_output_handle *handle,
}
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(event);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&event->lost_samples);
__output_copy(handle, values, n * sizeof(u64));
}
@@ -6217,7 +6228,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
{
struct perf_event *leader = event->group_leader, *sub;
u64 read_format = event->attr.read_format;
- u64 values[5];
+ u64 values[6];
int n = 0;
values[n++] = 1 + leader->nr_siblings;
@@ -6235,6 +6246,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
values[n++] = perf_event_count(leader);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&leader->lost_samples);
__output_copy(handle, values, n * sizeof(u64));
@@ -6248,6 +6261,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
values[n++] = perf_event_count(sub);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
+ if (read_format & PERF_FORMAT_LOST)
+ values[n++] = atomic64_read(&sub->lost_samples);
__output_copy(handle, values, n * sizeof(u64));
}
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2f6f77658eba2..ddcbd03eccbba 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -165,8 +165,10 @@ __perf_output_begin(struct perf_output_handle *handle,
goto out;
if (unlikely(rb->paused)) {
- if (rb->nr_pages)
+ if (rb->nr_pages) {
local_inc(&rb->lost);
+ atomic64_inc(&event->lost_samples);
+ }
goto out;
}
@@ -249,6 +251,7 @@ __perf_output_begin(struct perf_output_handle *handle,
fail:
local_inc(&rb->lost);
+ atomic64_inc(&event->lost_samples);
perf_output_put_handle(handle);
out:
rcu_read_unlock();
