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SubjectRe: [PATCH v1] perf record: Add an option to take an AUX snapshot on exit
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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@linux.intel.com>
> Co-developed-by: Adrian Hunter <adrian.hunter@intel.com>

checkpatch says:
WARNING: Co-developed-by: must be immediately followed by Signed-off-by

> ---
> 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);
>

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