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

From: Adrian Hunter
Date: Thu Sep 03 2020 - 06:44:45 EST

On 2/09/20 8:03 pm, Alexey Budankov wrote:
>
> 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.

There is a an existing debug print for snapshots, and the ack fifo of
course. So I am going to leave that for now.

>
> 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"
>>