Re: [PATCH V2 5/6] perf record: Add 'snapshot' control command

From: Alexey Budankov
Date: Wed Sep 02 2020 - 13:04:07 EST


On 01.09.2020 12:37, Adrian Hunter wrote:
> Add 'snapshot' control command to create an AUX area tracing snapshot the
> same as if sending SIGUSR2. The advantage of the FIFO is that access is
> governed by access to the FIFO.
>
> Example:
>
> $ mkfifo perf.control
> $ mkfifo perf.ack
> $ cat perf.ack &
> [1] 15235
> $ sudo ~/bin/perf record --control fifo:perf.control,perf.ack -S -e intel_pt//u -- sleep 60 &
> [2] 15243
> $ ps -e | grep perf
> 15244 pts/1 00:00:00 perf
> $ kill -USR2 15244
> bash: kill: (15244) - Operation not permitted
> $ echo snapshot > perf.control
> ack
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
> tools/perf/Documentation/perf-record.txt | 8 ++++----
> tools/perf/builtin-record.c | 24 +++++++++++++++++-------
> tools/perf/builtin-stat.c | 1 +
> tools/perf/util/evlist.c | 11 +++++++++--
> tools/perf/util/evlist.h | 5 ++++-
> 5 files changed, 35 insertions(+), 14 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 2ffc1196d2b8..588e6191bf39 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -631,10 +631,10 @@ endif::HAVE_LIBPFM[]
> --control=fd:ctl-fd[,ack-fd]::
> ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows.
> Listen on ctl-fd descriptor for command to control measurement ('enable': enable events,
> -'disable': disable events). Measurements can be started with events disabled using
> ---delay=-1 option. Optionally send control command completion ('ack\n') to ack-fd descriptor
> -to synchronize with the controlling process. Example of bash shell script to enable and
> -disable events during measurements:
> +'disable': disable events, 'snapshot': AUX area tracing snapshot). Measurements can be
> +started with events disabled using --delay=-1 option. Optionally send control command
> +completion ('ack\n') to ack-fd descriptor to synchronize with the controlling process.
> +Example of bash shell script to enable and disable events during measurements:
>
> #!/bin/bash
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 117dd180f780..476b34ff3152 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1593,6 +1593,16 @@ static int record__init_clock(struct record *rec)
> return 0;
> }
>
> +static void hit_auxtrace_snapshot_trigger(struct record *rec)
> +{
> + if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
> + trigger_hit(&auxtrace_snapshot_trigger);
> + auxtrace_record__snapshot_started = 1;
> + if (auxtrace_record__snapshot_start(rec->itr))
> + trigger_error(&auxtrace_snapshot_trigger);
> + }
> +}
> +
> static int __cmd_record(struct record *rec, int argc, const char **argv)
> {
> int err;
> @@ -1937,6 +1947,10 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> case EVLIST_CTL_CMD_DISABLE:
> pr_info(EVLIST_DISABLED_MSG);
> break;
> + case EVLIST_CTL_CMD_SNAPSHOT:
> + hit_auxtrace_snapshot_trigger(rec);

Could possibly print a messages to console that snapshot taking has started,
similar to enabling and disabling of events.

Acked-by: Alexei Budankov <alexey.budankov@xxxxxxxxxxxxxxx>

Regards,
Alexei

> + evlist__ctlfd_ack(rec->evlist);
> + break;
> case EVLIST_CTL_CMD_ACK:
> case EVLIST_CTL_CMD_UNSUPPORTED:
> default:
> @@ -2589,7 +2603,8 @@ static struct option __record_options[] = {
> parse_libpfm_events_option),
> #endif
> OPT_CALLBACK(0, "control", &record.opts, "fd:ctl-fd[,ack-fd] or fifo:ctl-fifo[,ack-fifo]",
> - "Listen on ctl-fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events).\n"
> + "Listen on ctl-fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events,\n"
> + "\t\t\t 'snapshot': AUX area tracing snapshot).\n"
> "\t\t\t Optionally send control command completion ('ack\\n') to ack-fd descriptor.\n"
> "\t\t\t Alternatively, ctl-fifo / ack-fifo will be opened and used as ctl-fd / ack-fd.",
> parse_control_option),
> @@ -2842,12 +2857,7 @@ static void snapshot_sig_handler(int sig __maybe_unused)
> {
> struct record *rec = &record;
>
> - if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
> - trigger_hit(&auxtrace_snapshot_trigger);
> - auxtrace_record__snapshot_started = 1;
> - if (auxtrace_record__snapshot_start(record.itr))
> - trigger_error(&auxtrace_snapshot_trigger);
> - }
> + hit_auxtrace_snapshot_trigger(rec);
>
> if (switch_output_signal(rec))
> trigger_hit(&switch_output_trigger);
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 6170226d44f9..21424ed0734b 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -578,6 +578,7 @@ static void process_evlist(struct evlist *evlist, unsigned int interval)
> process_interval();
> pr_info(EVLIST_DISABLED_MSG);
> break;
> + case EVLIST_CTL_CMD_SNAPSHOT:
> case EVLIST_CTL_CMD_ACK:
> case EVLIST_CTL_CMD_UNSUPPORTED:
> default:
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index b74e85bc683e..8cd53dbb0357 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1885,13 +1885,17 @@ static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
> } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
> (sizeof(EVLIST_CTL_CMD_DISABLE_TAG)-1))) {
> *cmd = EVLIST_CTL_CMD_DISABLE;
> + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_SNAPSHOT_TAG,
> + (sizeof(EVLIST_CTL_CMD_SNAPSHOT_TAG)-1))) {
> + *cmd = EVLIST_CTL_CMD_SNAPSHOT;
> + pr_debug("is snapshot\n");
> }
> }
>
> return bytes_read ? (int)bytes_read : err;
> }
>
> -static int evlist__ctlfd_ack(struct evlist *evlist)
> +int evlist__ctlfd_ack(struct evlist *evlist)
> {
> int err;
>
> @@ -1927,13 +1931,16 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
> case EVLIST_CTL_CMD_DISABLE:
> evlist__disable(evlist);
> break;
> + case EVLIST_CTL_CMD_SNAPSHOT:
> + break;
> case EVLIST_CTL_CMD_ACK:
> case EVLIST_CTL_CMD_UNSUPPORTED:
> default:
> pr_debug("ctlfd: unsupported %d\n", *cmd);
> break;
> }
> - if (!(*cmd == EVLIST_CTL_CMD_ACK || *cmd == EVLIST_CTL_CMD_UNSUPPORTED))
> + if (!(*cmd == EVLIST_CTL_CMD_ACK || *cmd == EVLIST_CTL_CMD_UNSUPPORTED ||
> + *cmd == EVLIST_CTL_CMD_SNAPSHOT))
> evlist__ctlfd_ack(evlist);
> }
> }
> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> index a5678eb5ee60..91d1da6e1fe3 100644
> --- a/tools/perf/util/evlist.h
> +++ b/tools/perf/util/evlist.h
> @@ -363,6 +363,7 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evlist,
> #define EVLIST_CTL_CMD_ENABLE_TAG "enable"
> #define EVLIST_CTL_CMD_DISABLE_TAG "disable"
> #define EVLIST_CTL_CMD_ACK_TAG "ack\n"
> +#define EVLIST_CTL_CMD_SNAPSHOT_TAG "snapshot"
>
> #define EVLIST_CTL_CMD_MAX_LEN 64
>
> @@ -370,7 +371,8 @@ enum evlist_ctl_cmd {
> EVLIST_CTL_CMD_UNSUPPORTED = 0,
> EVLIST_CTL_CMD_ENABLE,
> EVLIST_CTL_CMD_DISABLE,
> - EVLIST_CTL_CMD_ACK
> + EVLIST_CTL_CMD_ACK,
> + EVLIST_CTL_CMD_SNAPSHOT,
> };
>
> int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack, bool *ctl_fd_close);
> @@ -378,6 +380,7 @@ int evlist__initialize_ctlfd(struct evlist *evlist, int ctl_fd, int ctl_fd_ack);
> int evlist__finalize_ctlfd(struct evlist *evlist);
> bool evlist__ctlfd_initialized(struct evlist *evlist);
> int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd);
> +int evlist__ctlfd_ack(struct evlist *evlist);
>
> #define EVLIST_ENABLED_MSG "Events enabled\n"
> #define EVLIST_DISABLED_MSG "Events disabled\n"
>