Re: [PATCH 6/9] perf record: Support synthesizing cgroup events

From: Jiri Olsa
Date: Wed Jan 08 2020 - 17:09:05 EST

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On Tue, Jan 07, 2020 at 10:34:58PM +0900, Namhyung Kim wrote:
> 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.c | 3 +-
> tools/perf/util/cgroup.h | 1 +
> tools/perf/util/event.c | 1 +
> tools/perf/util/synthetic-events.c | 119 +++++++++++++++++++++++++++++
> tools/perf/util/synthetic-events.h | 1 +
> tools/perf/util/tool.h | 1 +
> 7 files changed, 129 insertions(+), 2 deletions(-)
>
> 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.c b/tools/perf/util/cgroup.c
> index 4e8ef1db0c94..5147d22b3bda 100644
> --- a/tools/perf/util/cgroup.c
> +++ b/tools/perf/util/cgroup.c
> @@ -15,8 +15,7 @@ int nr_cgroups;
>
> static struct rb_root cgroup_tree = RB_ROOT;
>
> -static int
> -cgroupfs_find_mountpoint(char *buf, size_t maxlen)
> +int cgroupfs_find_mountpoint(char *buf, size_t maxlen)

out of scope of this change, but could this be added to api/fs/fs.c?
it might need more checks then is currently supported, but would be
nice to have it under same api as the rest

jirka

> {
> FILE *fp;
> char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];
> diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h
> index 381583df27c7..9a67060723fa 100644
> --- a/tools/perf/util/cgroup.h
> +++ b/tools/perf/util/cgroup.h
> @@ -17,6 +17,7 @@ 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..36f122cac44f 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 +414,124 @@ 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;
> +
> + 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;
> + size_t mount_len; /* length of mount point in the path */
> + int ret = -1;
> +
> + cgrp_root = malloc(PATH_MAX);
> + if (cgrp_root == NULL)
> + return -1;
> +
> + if (cgroupfs_find_mountpoint(cgrp_root, PATH_MAX) < 0) {
> + pr_debug("cannot find cgroup mount point\n");
> + goto out;
> + }
> +
> + 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)
> + goto out;
> +
> + ret = 0;
> +
> +out:
> + free(cgrp_root);
> +
> + return ret;
> +}
> +
> 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;
> };
> --
> 2.24.1.735.g03f4e72817-goog
>

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