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Message-ID: <20230623082031.1402-1-ravi.bangoria@amd.com>
Date: Fri, 23 Jun 2023 13:50:31 +0530
From: Ravi Bangoria <ravi.bangoria@....com>
To: <acme@...nel.org>
CC: <ravi.bangoria@....com>, <jolsa@...nel.org>, <namhyung@...nel.org>,
<irogers@...gle.com>, <peterz@...radead.org>,
<adrian.hunter@...el.com>, <kan.liang@...el.com>,
<eranian@...gle.com>, <ak@...ux.intel.com>,
<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<sandipan.das@....com>, <ananth.narayan@....com>,
<santosh.shukla@....com>
Subject: [RFC] perf record: Use PERF_RECORD_LOST for synthesizing samples from read_format->lost
Currently perf synthesizes PERF_RECORD_LOST_SAMPLES samples for values
returned by read_format->lost. IIUC, PERF_RECORD_LOST_SAMPLES is used
only when hw provides corrupted samples and thus kernel has to drop
those. OTOH, PERF_RECORD_LOST is used when kernel has valid samples but
it fails to push them to ring-buffer because ring-buffer is already full.
So I feel PERF_RECORD_LOST is more appropriate for synthesizing samples
from read_format->lost.
Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
---
Notes:
- Posting this as RFC to get feedback. I haven't tested it well.
- There is one more minor issue: Aggregated Stats shows count of LOST/
LOST_SAMPLES records instead of actual number of lost events/samples:
```
$ sudo ./perf report -D | tail -20
Warning:
Processed 78923 events and lost 1153 chunks!
Warning:
Processed 47427 samples and lost 28.30%!
...
Aggregated stats:
LOST events: 1153 ( 1.5%)
LOST_SAMPLES events: 132 ( 0.2%)
```
Not sure if this is intentional.
tools/perf/builtin-record.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index efa03e4ac2c9..5baed42437b2 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1858,7 +1858,7 @@ record__switch_output(struct record *rec, bool at_exit)
}
static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
- struct perf_record_lost_samples *lost,
+ struct perf_record_lost *lost,
int cpu_idx, int thread_idx, u64 lost_count,
u16 misc_flag)
{
@@ -1871,6 +1871,7 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
sid = xyarray__entry(evsel->core.sample_id, cpu_idx, thread_idx);
sample.id = sid->id;
}
+ lost->id = sid->id;
id_hdr_size = perf_event__synthesize_id_sample((void *)(lost + 1),
evsel->core.attr.sample_type, &sample);
@@ -1882,7 +1883,7 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
static void record__read_lost_samples(struct record *rec)
{
struct perf_session *session = rec->session;
- struct perf_record_lost_samples *lost;
+ struct perf_record_lost *lost;
struct evsel *evsel;
/* there was an error during record__open */
@@ -1895,7 +1896,7 @@ static void record__read_lost_samples(struct record *rec)
return;
}
- lost->header.type = PERF_RECORD_LOST_SAMPLES;
+ lost->header.type = PERF_RECORD_LOST;
evlist__for_each_entry(session->evlist, evsel) {
struct xyarray *xy = evsel->core.sample_id;
--
2.41.0
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