This is just a prototype. Previous patch enables sharing hardware PMU among perf_events within same perf_event_context. This sharing comes with limitation that per CPU event cannot share hardware PMU with per task event. This limitation becomes a blocker when certain events could only use a specific PMU, for example, ref-cycles in some Intel CPUs. The following two commands will not share the PMU (when run in parallel):
perf stat -e ref-cycles -I 1000 perf stat -e ref-cycles -I 1000 --pid <pid> This patch shows a prototype that solves this problem with cgroup events. With this patch, the following two commands can share the PMU: perf stat -e ref-cycles -I 1000 perf stat -e ref-cycles -I 1000 --pid <pid> --create-cgroup The second command creates a cgroup for the pid, and move the pid to that cgroup. Then, a cgroup event (instead of task event) is created to monitor the process. Alternatively, we can also create a mechanism in the kernel that is very similar to cgroup perf events. I am also open to other suggestions. Signed-off-by: Song Liu <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Jiri Olsa <[email protected]> --- tools/perf/builtin-stat.c | 26 ++++++++++++++ tools/perf/util/cgroup.c | 76 +++++++++++++++++++++++++++++++++++++++ tools/perf/util/cgroup.h | 5 +++ tools/perf/util/target.h | 1 + 4 files changed, 108 insertions(+) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index b86aba1c8028..66a4da2d506e 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -646,6 +646,17 @@ static void print_counters(struct timespec *ts, int argc, const char **argv) ts, argc, argv); } +static void cleanup(void) +{ + /* clean up cgroups */ + if (target.create_cgroup) { + char name[32]; + + scnprintf(name, 31, "perf.%u", getpid()); + cgroup__cleanup(name); + } +} + static volatile int signr = -1; static void skip_signal(int signo) @@ -661,6 +672,7 @@ static void skip_signal(int signo) * and fast PID recycling */ child_pid = -1; + cleanup(); } static void sig_atexit(void) @@ -725,6 +737,8 @@ static const struct option stat_options[] = { "stat events on existing process id"), OPT_STRING('t', "tid", &target.tid, "tid", "stat events on existing thread id"), + OPT_BOOLEAN(0, "create-cgroup", &target.create_cgroup, + "create a cgroup for the pid/tid"), OPT_BOOLEAN('a', "all-cpus", &target.system_wide, "system-wide collection from all CPUs"), OPT_BOOLEAN('g', "group", &group, @@ -1607,6 +1621,17 @@ int cmd_stat(int argc, const char **argv) perf_stat__collect_metric_expr(evsel_list); perf_stat__init_shadow_stats(); + if (target.create_cgroup) { + char name[32]; + + scnprintf(name, 31, "perf.%u", getpid()); + cgroup__create(name); + cgroup__add_pid(name, strtoul(target.pid, NULL, 0)); + + cgroup__add_evlist(name, evsel_list); + target.pid = NULL; + } + if (stat_config.csv_sep) { stat_config.csv_output = true; if (!strcmp(stat_config.csv_sep, "\\t")) @@ -1906,5 +1931,6 @@ int cmd_stat(int argc, const char **argv) runtime_stat_delete(&stat_config); + cleanup(); return status; } diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c index ccd02634a616..f3e706f6fa96 100644 --- a/tools/perf/util/cgroup.c +++ b/tools/perf/util/cgroup.c @@ -249,3 +249,79 @@ int parse_cgroups(const struct option *opt, const char *str, } return 0; } + +int cgroup__add_evlist(const char *name, struct perf_evlist *evlist) +{ + return add_cgroup(evlist, name); +} + +int cgroup__create(const char *name) +{ + char path[PATH_MAX + 1]; + char mnt[PATH_MAX + 1]; + + if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1)) + return -1; + + scnprintf(path, PATH_MAX, "%s/%s", mnt, name); + + return mkdir(path, 0755); +} + +int cgroup__add_pid(const char *name, pid_t pid) +{ + char path[PATH_MAX + 1]; + char mnt[PATH_MAX + 1]; + char buf[32]; + int fd; + + if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1)) + return -1; + + scnprintf(path, PATH_MAX, "%s/%s/cgroup.procs", mnt, name); + fd = open(path, O_WRONLY); + if (fd < 0) + return -1; + scnprintf(buf, 31, "%u", pid); + if (write(fd, buf, strlen(buf)) < 0) + fprintf(stderr, "Error writing %s to %s\n", buf, path); + + close(fd); + return 0; +} + +int cgroup__cleanup(const char *name) +{ + char path[PATH_MAX + 1]; + char mnt[PATH_MAX + 1]; + char *line; + size_t len = 0; + FILE *fp; + int fd; + + if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1)) + return -1; + + scnprintf(path, PATH_MAX, "%s/%s/cgroup.procs", mnt, name); + fp = fopen(path, "r"); + + if (fp == NULL) + return -1; + + scnprintf(path, PATH_MAX, "%s/cgroup.procs", mnt); + fd = open(path, O_WRONLY); + if (fd < 0) { + fclose(fp); + return -1; + } + + while (getline(&line, &len, fp) != -1) { + if (write(fd, line, strlen(line)) < 0) + fprintf(stderr, "Error writing %s to %s\n", line, path); + } + close(fd); + fclose(fp); + + scnprintf(path, PATH_MAX, "%s/%s", mnt, name); + return rmdir(path); +} diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h index f033a80c1b14..7bdd8d99d130 100644 --- a/tools/perf/util/cgroup.h +++ b/tools/perf/util/cgroup.h @@ -26,4 +26,9 @@ void evlist__set_default_cgroup(struct perf_evlist *evlist, struct cgroup *cgrou int parse_cgroups(const struct option *opt, const char *str, int unset); +int cgroup__create(const char *name); +int cgroup__cleanup(const char *name); +int cgroup__add_pid(const char *name, pid_t pid); +int cgroup__add_evlist(const char *name, struct perf_evlist *evlist); + #endif /* __CGROUP_H__ */ diff --git a/tools/perf/util/target.h b/tools/perf/util/target.h index 6ef01a83b24e..03c9ac06660a 100644 --- a/tools/perf/util/target.h +++ b/tools/perf/util/target.h @@ -15,6 +15,7 @@ struct target { bool uses_mmap; bool default_per_cpu; bool per_thread; + bool create_cgroup; }; enum target_errno { -- 2.17.1
