[PATCH 07/10] perf record: Support synthesizing cgroup events

From: Namhyung Kim
Date: Sun Feb 23 2020 - 23:38:44 EST


Synthesize cgroup events by iterating cgroup filesystem directories.
The cgroup event only saves the portion of cgroup path after the mount
point and the cgroup id (which actually is a file handle).

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
tools/perf/builtin-record.c | 5 ++
tools/perf/util/cgroup.h | 1 +
tools/perf/util/event.c | 1 +
tools/perf/util/synthetic-events.c | 113 +++++++++++++++++++++++++++++
tools/perf/util/synthetic-events.h | 1 +
tools/perf/util/tool.h | 1 +
6 files changed, 122 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 4c301466101b..2802de9538ff 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1397,6 +1397,11 @@ static int record__synthesize(struct record *rec, bool tail)
if (err < 0)
pr_warning("Couldn't synthesize bpf events.\n");

+ err = perf_event__synthesize_cgroups(tool, process_synthesized_event,
+ machine);
+ if (err < 0)
+ pr_warning("Couldn't synthesize cgroup events.\n");
+
err = __machine__synthesize_threads(machine, tool, &opts->target, rec->evlist->core.threads,
process_synthesized_event, opts->sample_address,
1);
diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h
index e98d5975fe55..8337ec452c66 100644
--- a/tools/perf/util/cgroup.h
+++ b/tools/perf/util/cgroup.h
@@ -18,6 +18,7 @@ struct cgroup {

extern int nr_cgroups; /* number of explicit cgroups defined */

+int cgroupfs_find_mountpoint(char *buf, size_t maxlen);
struct cgroup *cgroup__get(struct cgroup *cgroup);
void cgroup__put(struct cgroup *cgroup);

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 824c038e5c33..28801c867f39 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -33,6 +33,7 @@
#include "bpf-event.h"
#include "tool.h"
#include "../perf.h"
+#include "cgroup.h"

static const char *perf_event__names[] = {
[0] = "TOTAL",
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index cd336eb8886b..e826ccad1ebd 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -16,6 +16,7 @@
#include "util/synthetic-events.h"
#include "util/target.h"
#include "util/time-utils.h"
+#include "util/cgroup.h"
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/string.h>
@@ -413,6 +414,118 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
return rc;
}

+static int perf_event__synthesize_cgroup(struct perf_tool *tool,
+ union perf_event *event,
+ char *path, size_t mount_len,
+ perf_event__handler_t process,
+ struct machine *machine)
+{
+ size_t event_size = sizeof(event->cgroup) - sizeof(event->cgroup.path);
+ size_t path_len = strlen(path) - mount_len + 1;
+ struct {
+ struct file_handle fh;
+ uint64_t cgroup_id;
+ } handle;
+ int mount_id;
+
+ while (path_len % sizeof(u64))
+ path[mount_len + path_len++] = '\0';
+
+ memset(&event->cgroup, 0, event_size);
+
+ event->cgroup.header.type = PERF_RECORD_CGROUP;
+ event->cgroup.header.size = event_size + path_len + machine->id_hdr_size;
+
+ handle.fh.handle_bytes = sizeof(handle.cgroup_id);
+ if (name_to_handle_at(AT_FDCWD, path, &handle.fh, &mount_id, 0) < 0) {
+ pr_debug("stat failed: %s\n", path);
+ return -1;
+ }
+
+ event->cgroup.id = handle.cgroup_id;
+ strncpy(event->cgroup.path, path + mount_len, path_len);
+ memset(event->cgroup.path + path_len, 0, machine->id_hdr_size);
+
+ if (perf_tool__process_synth_event(tool, event, machine, process) < 0) {
+ pr_debug("process synth event failed\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+static int perf_event__walk_cgroup_tree(struct perf_tool *tool,
+ union perf_event *event,
+ char *path, size_t mount_len,
+ perf_event__handler_t process,
+ struct machine *machine)
+{
+ size_t pos = strlen(path);
+ DIR *d;
+ struct dirent *dent;
+ int ret = 0;
+
+ if (perf_event__synthesize_cgroup(tool, event, path, mount_len,
+ process, machine) < 0)
+ return -1;
+
+ d = opendir(path);
+ if (d == NULL) {
+ pr_debug("failed to open directory: %s\n", path);
+ return -1;
+ }
+
+ while ((dent = readdir(d)) != NULL) {
+ if (dent->d_type != DT_DIR)
+ continue;
+ if (!strcmp(dent->d_name, ".") ||
+ !strcmp(dent->d_name, ".."))
+ continue;
+
+ /* any sane path should be less than PATH_MAX */
+ if (strlen(path) + strlen(dent->d_name) + 1 >= PATH_MAX)
+ continue;
+
+ if (path[pos - 1] != '/')
+ strcat(path, "/");
+ strcat(path, dent->d_name);
+
+ ret = perf_event__walk_cgroup_tree(tool, event, path,
+ mount_len, process, machine);
+ if (ret < 0)
+ break;
+
+ path[pos] = '\0';
+ }
+
+ closedir(d);
+ return ret;
+}
+
+int perf_event__synthesize_cgroups(struct perf_tool *tool,
+ perf_event__handler_t process,
+ struct machine *machine)
+{
+ union perf_event event;
+ char cgrp_root[PATH_MAX];
+ size_t mount_len; /* length of mount point in the path */
+
+ if (cgroupfs__mountpoint(cgrp_root, PATH_MAX, "perf_event") < 0) {
+ pr_debug("cannot find cgroup mount point\n");
+ return -1;
+ }
+
+ mount_len = strlen(cgrp_root);
+ /* make sure the path starts with a slash (after mount point) */
+ strcat(cgrp_root, "/");
+
+ if (perf_event__walk_cgroup_tree(tool, &event, cgrp_root, mount_len,
+ process, machine) < 0)
+ return -1;
+
+ return 0;
+}
+
int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t process,
struct machine *machine)
{
diff --git a/tools/perf/util/synthetic-events.h b/tools/perf/util/synthetic-events.h
index baead0cdc381..e7a3e9589738 100644
--- a/tools/perf/util/synthetic-events.h
+++ b/tools/perf/util/synthetic-events.h
@@ -45,6 +45,7 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool, perf_event__handl
int perf_event__synthesize_mmap_events(struct perf_tool *tool, union perf_event *event, pid_t pid, pid_t tgid, perf_event__handler_t process, struct machine *machine, bool mmap_data);
int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_namespaces(struct perf_tool *tool, union perf_event *event, pid_t pid, pid_t tgid, perf_event__handler_t process, struct machine *machine);
+int perf_event__synthesize_cgroups(struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_format, const struct perf_sample *sample);
int perf_event__synthesize_stat_config(struct perf_tool *tool, struct perf_stat_config *config, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_stat_events(struct perf_stat_config *config, struct perf_tool *tool, struct evlist *evlist, perf_event__handler_t process, bool attrs);
diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h
index 472ef5eb4068..3fb67bd31e4a 100644
--- a/tools/perf/util/tool.h
+++ b/tools/perf/util/tool.h
@@ -79,6 +79,7 @@ struct perf_tool {
bool ordered_events;
bool ordering_requires_timestamps;
bool namespace_events;
+ bool cgroup_events;
bool no_warn;
enum show_feature_header show_feat_hdr;
};
--
2.25.0.265.gbab2e86ba0-goog