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Subject[tip:perf/core] perf record: Record the first and last sample time in the header
Commit-ID:  68588baf8d01826673f2874f434123029e519052
Author: Jin Yao <>
AuthorDate: Fri, 8 Dec 2017 21:13:42 +0800
Committer: Arnaldo Carvalho de Melo <>
CommitDate: Mon, 8 Jan 2018 11:20:56 -0300

perf record: Record the first and last sample time in the header

In the default 'perf record' configuration, all samples are processed,
to create the HEADER_BUILD_ID table. So it's very easy to get the
first/last samples and save the time to perf file header via the
function write_sample_time().

Later, at post processing time, perf report/script will fetch the time
from perf file header.

Committer testing:

# perf record -a sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 2.099 MB (1101 samples) ]
[root@jouet home]# perf report --header | grep "time of "
# time of first sample : 22947.909226
# time of last sample : 22948.910704
# perf report -D | grep PERF_RECORD_SAMPLE\(
0 22947909226101 0x20bb68 [0x30]: PERF_RECORD_SAMPLE(IP, 0x4001): 0/0: 0xffffffffa21b1af3 period: 1 addr: 0
0 22947909229928 0x20bb98 [0x30]: PERF_RECORD_SAMPLE(IP, 0x4001): 0/0: 0xffffffffa200d204 period: 1 addr: 0
3 22948910397351 0x219360 [0x30]: PERF_RECORD_SAMPLE(IP, 0x4001): 28251/28251: 0xffffffffa22071d8 period: 169518 addr: 0
0 22948910652380 0x20f120 [0x30]: PERF_RECORD_SAMPLE(IP, 0x4001): 0/0: 0xffffffffa2856816 period: 198807 addr: 0
2 22948910704034 0x2172d0 [0x30]: PERF_RECORD_SAMPLE(IP, 0x4001): 0/0: 0xffffffffa2856816 period: 88111 addr: 0


v7: Just update the patch description according to Arnaldo's suggestion.

v6: Currently '--buildid-all' is not enabled at default. So the walking
on all samples is the default operation. There is no big overhead
to calculate the timestamp boundary in process_sample_event handler
once we already go through all samples. So the timestamp boundary
calculation is enabled by default when '--buildid-all' is not enabled.

While if '--buildid-all' is enabled, we creates a new option
"--timestamp-boundary" for user to decide if it enables the
timestamp boundary calculation.

v5: There is an issue that the sample walking can only work when
'--buildid-all' is not enabled. So we need to let the walking
be able to work even if '--buildid-all' is enabled and let the
processing skips the dso hit marking for this case.

At first, I want to provide a new option "--record-time-boundaries".
While after consideration, I think a new option is not very

v3: Remove the definitions of first_sample_time and last_sample_time
from struct record and directly save them in perf_evlist.

Signed-off-by: Jin Yao <>
Acked-by: Jiri Olsa <>
Tested-by: Arnaldo Carvalho de Melo <>
Cc: Alexander Shishkin <>
Cc: Andi Kleen <>
Cc: Kan Liang <>
Cc: Peter Zijlstra <>
Signed-off-by: Arnaldo Carvalho de Melo <>
tools/perf/Documentation/perf-record.txt | 3 +++
tools/perf/builtin-record.c | 18 +++++++++++++++---
2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5a626ef..3eea6de 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -430,6 +430,9 @@ Configure all used events to run in user space.
Append timestamp to output file name.

+Record timestamp boundary (time of first/last samples).
Generate multiple files, timestamp prefixed, switching to a new one
based on 'mode' value:
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 50385d8..65681a1 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -78,6 +78,7 @@ struct record {
bool no_buildid_cache_set;
bool buildid_all;
bool timestamp_filename;
+ bool timestamp_boundary;
struct switch_output switch_output;
unsigned long long samples;
@@ -409,8 +410,15 @@ static int process_sample_event(struct perf_tool *tool,
struct record *rec = container_of(tool, struct record, tool);

- rec->samples++;
+ if (rec->evlist->first_sample_time == 0)
+ rec->evlist->first_sample_time = sample->time;
+ rec->evlist->last_sample_time = sample->time;

+ if (rec->buildid_all)
+ return 0;
+ rec->samples++;
return build_id__mark_dso_hit(tool, event, sample, evsel, machine);

@@ -435,9 +443,11 @@ static int process_buildids(struct record *rec)

* If --buildid-all is given, it marks all DSO regardless of hits,
- * so no need to process samples.
+ * so no need to process samples. But if timestamp_boundary is enabled,
+ * it still needs to walk on all samples to get the timestamps of
+ * first/last samples.
- if (rec->buildid_all)
+ if (rec->buildid_all && !rec->timestamp_boundary)
rec->tool.sample = NULL;

return perf_session__process_events(session);
@@ -1621,6 +1631,8 @@ static struct option __record_options[] = {
"Record build-id of all DSOs regardless of hits"),
OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
"append timestamp to output filename"),
+ OPT_BOOLEAN(0, "timestamp-boundary", &record.timestamp_boundary,
+ "Record timestamp boundary (time of first/last samples)"),
OPT_STRING_OPTARG_SET(0, "switch-output", &record.switch_output.str,
&record.switch_output.set, "signal,size,time",
"Switch output when receive SIGUSR2 or cross size,time threshold",
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