[PATCH v10 12/15] perf stat: introduce --control fd:ctl-fd[,ack-fd] options

Alexey Budankov
2020-07-08T07:54:11Z

Introduce --control fd:ctl-fd[,ack-fd] options to pass open file
descriptors numbers from command line. Extend perf-stat.txt file
with --control fd:ctl-fd[,ack-fd] options description. Document
possible usage model introduced by --control fd:ctl-fd[,ack-fd]
options by providing example bash shell script.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
tools/perf/Documentation/perf-stat.txt | 39 +++++++++++++++++++++++++
tools/perf/builtin-stat.c | 40 +++++++++++++++++++++++++-
tools/perf/util/stat.h | 2 ++
3 files changed, 80 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 9f32f6cd558d..c9bfefc051fb 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -176,6 +176,45 @@ with it. --append may be used here. Examples:
3>results perf stat --log-fd 3 -- $cmd
3>>results perf stat --log-fd 3 --append -- $cmd

+--control fd:ctl-fd[,ack-fd]
+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:
+
+#!/bin/bash
+
+ctl_dir=/tmp/
+
+ctl_fifo=${ctl_dir}perf_ctl.fifo
+test -p ${ctl_fifo} && unlink ${ctl_fifo}
+mkfifo ${ctl_fifo}
+exec {ctl_fd}<>${ctl_fifo}
+
+ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo
+test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
+mkfifo ${ctl_ack_fifo}
+exec {ctl_fd_ack}<>${ctl_ack_fifo}
+
+perf stat -D -1 -e cpu-cycles -a -I 1000 \
+ --control fd:${ctl_fd},${ctl_fd_ack} \
+ -- sleep 30 &
+perf_pid=$!
+
+sleep 5 && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
+sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"
+
+exec {ctl_fd_ack}>&-
+unlink ${ctl_ack_fifo}
+
+exec {ctl_fd}>&-
+unlink ${ctl_fifo}
+
+wait -n ${perf_pid}
+exit $?
+
+
--pre::
--post::
Pre and post measurement hooks, e.g.:
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 5280a45af5dc..483a28ef4ec4 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -188,6 +188,8 @@ static struct perf_stat_config stat_config = {
.metric_only_len = METRIC_ONLY_LEN,
.walltime_nsecs_stats = &walltime_nsecs_stats,
.big_num = true,
+ .ctl_fd = -1,
+ .ctl_fd_ack = -1
};

static bool cpus_map_matched(struct evsel *a, struct evsel *b)
@@ -867,7 +869,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
perf_evlist__start_workload(evsel_list);
enable_counters();

- if (interval || timeout)
+ if (interval || timeout || evlist__ctlfd_initialized(evsel_list))
status = dispatch_events(forks, timeout, interval, &times);
if (child_pid != -1) {
if (timeout)
@@ -1039,6 +1041,33 @@ static int parse_metric_groups(const struct option *opt,
&stat_config.metric_events);
}

+static int parse_control_option(const struct option *opt,
+ const char *str,
+ int unset __maybe_unused)
+{
+ char *comma = NULL, *endptr = NULL;
+ struct perf_stat_config *config = (struct perf_stat_config *)opt->value;
+
+ if (strncmp(str, "fd:", 3))
+ return -EINVAL;
+
+ config->ctl_fd = strtoul(&str[3], &endptr, 0);
+ if (endptr == &str[3])
+ return -EINVAL;
+
+ comma = strchr(str, ',');
+ if (comma) {
+ if (endptr != comma)
+ return -EINVAL;
+
+ config->ctl_fd_ack = strtoul(comma + 1, &endptr, 0);
+ if (endptr == comma + 1 || *endptr != '\0')
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static struct option stat_options[] = {
OPT_BOOLEAN('T', "transaction", &transaction_run,
"hardware transaction statistics"),
@@ -1140,6 +1169,10 @@ static struct option stat_options[] = {
"libpfm4 event selector. use 'perf list' to list available events",
parse_libpfm_events_option),
#endif
+ OPT_CALLBACK(0, "control", &stat_config, "fd:ctl-fd[,ack-fd]",
+ "Listen on ctl-fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events).\n"
+ "\t\t\t Optionally send control command completion ('ack\\n') to ack-fd descriptor.",
+ parse_control_option),
OPT_END()
};

@@ -2309,6 +2342,9 @@ int cmd_stat(int argc, const char **argv)
signal(SIGALRM, skip_signal);
signal(SIGABRT, skip_signal);

+ if (evlist__initialize_ctlfd(evsel_list, stat_config.ctl_fd, stat_config.ctl_fd_ack))
+ goto out;
+
status = 0;
for (run_idx = 0; forever || run_idx < stat_config.run_count; run_idx++) {
if (stat_config.run_count != 1 && verbose > 0)
@@ -2328,6 +2364,8 @@ int cmd_stat(int argc, const char **argv)
if (!forever && status != -1 && (!interval || stat_config.summary))
print_counters(NULL, argc, argv);

+ evlist__finalize_ctlfd(evsel_list);
+
if (STAT_RECORD) {
/*
* We synthesize the kernel mmap record just so that older tools
diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
index 41d59f192931..f8778cffd941 100644
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -133,6 +133,8 @@ struct perf_stat_config {
struct perf_cpu_map *cpus_aggr_map;
u64 *walltime_run;
struct rblist metric_events;
+ int ctl_fd;
+ int ctl_fd_ack;
};

void perf_stat__set_big_num(int set);
--
2.24.1