Re: [PATCH v1] perf record: Add an option to take an AUX snapshot on exit

From: Arnaldo Carvalho de Melo
Date: Wed Aug 07 2019 - 09:03:59 EST

Em Wed, Aug 07, 2019 at 10:40:39AM +0300, Adrian Hunter escreveu:
> On 6/08/19 5:41 PM, Alexander Shishkin wrote:
> > It is sometimes useful to generate a snapshot when perf record exits;
> > I've been using a wrapper script around the workload that would do a
> > killall -USR2 perf when the workload exits.
> >
> > This patch makes it easier and also works when perf record is attached
> > to a pre-existing task. A new snapshot option 'e' can be specified in
> > -S to enable this behavior:
> >
> > root@elsewhere:~# perf record -e intel_pt// -Se sleep 1
> > [ perf record: Woken up 2 times to write data ]
> > [ perf record: Captured and wrote 0.085 MB perf.data ]
> >
> > Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> > Co-developed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>
> checkpatch says:
> WARNING: Co-developed-by: must be immediately followed by Signed-off-by

I can fix this.

- Arnaldo

> > ---
> > tools/perf/Documentation/perf-record.txt | 11 +++++---
> > tools/perf/builtin-record.c | 34 +++++++++++++++++++++---
> > tools/perf/perf.h | 1 +
> > tools/perf/util/auxtrace.c | 14 ++++++++--
> > tools/perf/util/auxtrace.h | 2 +-
> > 5 files changed, 52 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> > index 15e0fa87241b..d5e58e0a2bca 100644
> > --- a/tools/perf/Documentation/perf-record.txt
> > +++ b/tools/perf/Documentation/perf-record.txt
> > @@ -422,9 +422,14 @@ CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI.
> > -S::
> > --snapshot::
> > Select AUX area tracing Snapshot Mode. This option is valid only with an
> > -AUX area tracing event. Optionally the number of bytes to capture per
> > -snapshot can be specified. In Snapshot Mode, trace data is captured only when
> > -signal SIGUSR2 is received.
> > +AUX area tracing event. Optionally, certain snapshot capturing parameters
> > +can be specified in a string that follows this option:
> > + 'e': take one last snapshot on exit; guarantees that there is at least one
> > + snapshot in the output file;
> > + <size>: if the PMU supports this, specify the desired snapshot size.
> > +
> > +In Snapshot Mode trace data is captured only when signal SIGUSR2 is received
> > +and on exit if the above 'e' option is given.
> >
> > --proc-map-timeout::
> > When processing pre-existing threads /proc/XXX/mmap, it may take a long time,
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index d31d7a5a1be3..e9a2525ecfcc 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -613,19 +613,35 @@ static int record__auxtrace_read_snapshot_all(struct record *rec)
> > return rc;
> > }
> >
> > -static void record__read_auxtrace_snapshot(struct record *rec)
> > +static void record__read_auxtrace_snapshot(struct record *rec, bool on_exit)
> > {
> > pr_debug("Recording AUX area tracing snapshot\n");
> > if (record__auxtrace_read_snapshot_all(rec) < 0) {
> > trigger_error(&auxtrace_snapshot_trigger);
> > } else {
> > - if (auxtrace_record__snapshot_finish(rec->itr))
> > + if (auxtrace_record__snapshot_finish(rec->itr, on_exit))
> > trigger_error(&auxtrace_snapshot_trigger);
> > else
> > trigger_ready(&auxtrace_snapshot_trigger);
> > }
> > }
> >
> > +static int record__auxtrace_snapshot_exit(struct record *rec)
> > +{
> > + if (trigger_is_error(&auxtrace_snapshot_trigger))
> > + return 0;
> > +
> > + if (!auxtrace_record__snapshot_started &&
> > + auxtrace_record__snapshot_start(rec->itr))
> > + return -1;
> > +
> > + record__read_auxtrace_snapshot(rec, true);
>
> Buffers can get un-mapped earlier as tasks exit. Refer
> perf_evlist__filter_pollfd() -> perf_evlist__munmap_filtered().
> Maybe we should prevent that for this case.
> e.g. do perf_mmap__get()'s on the mmaps at the start, and then 'put' them
> all here.
>
> > + if (trigger_is_error(&auxtrace_snapshot_trigger))
> > + return -1;
> > +
> > + return 0;
> > +}
> > +
> > static int record__auxtrace_init(struct record *rec)
> > {
> > int err;
> > @@ -654,7 +670,7 @@ int record__auxtrace_mmap_read(struct record *rec __maybe_unused,
> > }
> >
> > static inline
> > -void record__read_auxtrace_snapshot(struct record *rec __maybe_unused)
> > +void record__read_auxtrace_snapshot(struct record *rec __maybe_unused, bool on_exit)
> > {
> > }
> >
> > @@ -664,6 +680,12 @@ int auxtrace_record__snapshot_start(struct auxtrace_record *itr __maybe_unused)
> > return 0;
> > }
> >
> > +static inline
> > +int record__auxtrace_snapshot_exit(struct record *rec)
> > +{
> > + return 0;
> > +}
> > +
> > static int record__auxtrace_init(struct record *rec __maybe_unused)
> > {
> > return 0;
> > @@ -1536,7 +1558,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> > if (auxtrace_record__snapshot_started) {
> > auxtrace_record__snapshot_started = 0;
> > if (!trigger_is_error(&auxtrace_snapshot_trigger))
> > - record__read_auxtrace_snapshot(rec);
> > + record__read_auxtrace_snapshot(rec, false);
> > if (trigger_is_error(&auxtrace_snapshot_trigger)) {
> > pr_err("AUX area tracing snapshot failed\n");
> > err = -1;
> > @@ -1609,9 +1631,13 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> > disabled = true;
> > }
> > }
> > +
> > trigger_off(&auxtrace_snapshot_trigger);
> > trigger_off(&switch_output_trigger);
> >
> > + if (opts->auxtrace_snapshot_on_exit)
> > + record__auxtrace_snapshot_exit(rec);
> > +
> > if (forks && workload_exec_errno) {
> > char msg[STRERR_BUFSIZE];
> > const char *emsg = str_error_r(workload_exec_errno, msg, sizeof(msg));
> > diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> > index 74d0124d38f3..dc0a7a237887 100644
> > --- a/tools/perf/perf.h
> > +++ b/tools/perf/perf.h
> > @@ -57,6 +57,7 @@ struct record_opts {
> > bool running_time;
> > bool full_auxtrace;
> > bool auxtrace_snapshot_mode;
> > + bool auxtrace_snapshot_on_exit;
> > bool record_namespaces;
> > bool record_switch_events;
> > bool all_kernel;
> > diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> > index 65728cdeefb6..72ce4c5e7c78 100644
> > --- a/tools/perf/util/auxtrace.c
> > +++ b/tools/perf/util/auxtrace.c
> > @@ -539,9 +539,9 @@ int auxtrace_record__snapshot_start(struct auxtrace_record *itr)
> > return 0;
> > }
> >
> > -int auxtrace_record__snapshot_finish(struct auxtrace_record *itr)
> > +int auxtrace_record__snapshot_finish(struct auxtrace_record *itr, bool on_exit)
> > {
> > - if (itr && itr->snapshot_finish)
> > + if (!on_exit && itr && itr->snapshot_finish)
>
> You are assuming you know what every ->snapshot_finish() does. It would be
> better to pass on_exit to ->snapshot_finish().
>
> > return itr->snapshot_finish(itr);
> > return 0;
> > }
> > @@ -577,6 +577,16 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
> > if (!str)
> > return 0;
> >
> > + /* PMU-agnostic options */
> > + switch (*str) {
> > + case 'e':
> > + opts->auxtrace_snapshot_on_exit = true;
> > + str++;
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > if (itr)
> > return itr->parse_snapshot_options(itr, opts, str);
> >
> > diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> > index 17eb04a1da4d..8ccabacd0b11 100644
> > --- a/tools/perf/util/auxtrace.h
> > +++ b/tools/perf/util/auxtrace.h
> > @@ -499,7 +499,7 @@ int auxtrace_record__info_fill(struct auxtrace_record *itr,
> > size_t priv_size);
> > void auxtrace_record__free(struct auxtrace_record *itr);
> > int auxtrace_record__snapshot_start(struct auxtrace_record *itr);
> > -int auxtrace_record__snapshot_finish(struct auxtrace_record *itr);
> > +int auxtrace_record__snapshot_finish(struct auxtrace_record *itr, bool on_exit);
> > int auxtrace_record__find_snapshot(struct auxtrace_record *itr, int idx,
> > struct auxtrace_mmap *mm,
> > unsigned char *data, u64 *head, u64 *old);
> >