Hi all!
Please let me know if there are any specific guidelines or requirements
you would like me to consider while reviewing the work. I am open to any
suggestions or comments you may have.
Appreciate any feedback on that.
On Fri, Oct 13, 2023 at 09:41:07PM +0300, Dmitry Rokosov wrote:
> This is a simple listener for memory events that handles counter
> changes in runtime. It can be set up for a specific memory cgroup v2.
>
> The output example:
> =====
> $ /tmp/cgroup_v2_event_listener test
> Initialized MEMCG events with counters:
> MEMCG events:
> low: 0
> high: 0
> max: 0
> oom: 0
> oom_kill: 0
> oom_group_kill: 0
> Started monitoring memory events from '/sys/fs/cgroup/test/memory.events'...
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 0 => 1
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 1 => 2
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 2 => 3
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 3 => 4
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 2 MEMCG max events, change counter 0 => 2
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 8 MEMCG max events, change counter 2 => 10
> *** 1 MEMCG oom event, change counter 0 => 1
> Received event in /sys/fs/cgroup/test/memory.events:
> *** 1 MEMCG oom_kill event, change counter 4 => 5
> ^CExiting cgroup v2 event listener...
> =====
>
> Signed-off-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxxxxx>
> ---
> tools/cgroup/Makefile | 4 +-
> tools/cgroup/cgroup_v2_event_listener.c | 330 ++++++++++++++++++++++++
> 2 files changed, 332 insertions(+), 2 deletions(-)
> create mode 100644 tools/cgroup/cgroup_v2_event_listener.c
>
> diff --git a/tools/cgroup/Makefile b/tools/cgroup/Makefile
> index ffca068e4a76..86bd357a8f54 100644
> --- a/tools/cgroup/Makefile
> +++ b/tools/cgroup/Makefile
> @@ -3,9 +3,9 @@
>
> CFLAGS = -Wall -Wextra
>
> -all: cgroup_event_listener
> +all: cgroup_event_listener cgroup_v2_event_listener
> %: %.c
> $(CC) $(CFLAGS) -o $@ $^
>
> clean:
> - $(RM) cgroup_event_listener
> + $(RM) cgroup_event_listener cgroup_v2_event_listener
> diff --git a/tools/cgroup/cgroup_v2_event_listener.c b/tools/cgroup/cgroup_v2_event_listener.c
> new file mode 100644
> index 000000000000..987261db5369
> --- /dev/null
> +++ b/tools/cgroup/cgroup_v2_event_listener.c
> @@ -0,0 +1,330 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * cgroup_v2_event_listener.c - Simple listener of cgroup v2 memory.events
> + *
> + * Copyright (c) 2023, SaluteDevices. All Rights Reserved.
> + *
> + * Author: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxxxxx>
> + */
> +
> +#include <err.h>
> +#include <errno.h>
> +#include <limits.h>
> +#include <poll.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/inotify.h>
> +#include <unistd.h>
> +
> +#define MEMCG_EVENTS "memory.events"
> +
> +/* Size of buffer to use when reading inotify events */
> +#define INOTIFY_BUFFER_SIZE 8192
> +
> +#define INOTIFY_EVENT_NEXT(event, length) ({ \
> + (length) -= sizeof(*(event)) + (event)->len; \
> + (event)++; \
> +})
> +
> +#define INOTIFY_EVENT_OK(event, length) ((length) >= (ssize_t)sizeof(*(event)))
> +
> +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
> +
> +struct memcg_counters {
> + long low;
> + long high;
> + long max;
> + long oom;
> + long oom_kill;
> + long oom_group_kill;
> +};
> +
> +struct memcg_events {
> + struct memcg_counters counters;
> + char path[PATH_MAX];
> + int inotify_fd;
> + int inotify_wd;
> +};
> +
> +static void print_memcg_counters(const struct memcg_counters *counters)
> +{
> + printf("MEMCG events:\n");
> + printf("\tlow: %ld\n", counters->low);
> + printf("\thigh: %ld\n", counters->high);
> + printf("\tmax: %ld\n", counters->max);
> + printf("\toom: %ld\n", counters->oom);
> + printf("\toom_kill: %ld\n", counters->oom_kill);
> + printf("\toom_group_kill: %ld\n", counters->oom_group_kill);
> +}
> +
> +static int get_memcg_counter(char *line, const char *name, long *counter)
> +{
> + size_t len = strlen(name);
> + char *endptr;
> + long tmp;
> +
> + if (memcmp(line, name, len)) {
> + warnx("Counter line %s has wrong name, %s is expected",
> + line, name);
> + return -EINVAL;
> + }
> +
> + /* skip the whitespace delimiter */
> + len += 1;
> +
> + errno = 0;
> + tmp = strtol(&line[len], &endptr, 10);
> + if (((tmp == LONG_MAX || tmp == LONG_MIN) && errno == ERANGE) ||
> + (errno && !tmp)) {
> + warnx("Failed to parse: %s", &line[len]);
> + return -ERANGE;
> + }
> +
> + if (endptr == &line[len]) {
> + warnx("Not digits were found in line %s", &line[len]);
> + return -EINVAL;
> + }
> +
> + if (!(*endptr == '\0' || (*endptr == '\n' && *++endptr == '\0'))) {
> + warnx("Further characters after number: %s", endptr);
> + return -EINVAL;
> + }
> +
> + *counter = tmp;
> +
> + return 0;
> +}
> +
> +static int read_memcg_events(struct memcg_events *events, bool show_diff)
> +{
> + FILE *fp = fopen(events->path, "re");
> + size_t i;
> + int ret = 0;
> + bool any_new_events = false;
> + char *line = NULL;
> + size_t len = 0;
> + struct memcg_counters new_counters;
> + struct memcg_counters *counters = &events->counters;
> + struct {
> + const char *name;
> + long *new;
> + long *old;
> + } map[] = {
> + {
> + .name = "low",
> + .new = &new_counters.low,
> + .old = &counters->low,
> + },
> + {
> + .name = "high",
> + .new = &new_counters.high,
> + .old = &counters->high,
> + },
> + {
> + .name = "max",
> + .new = &new_counters.max,
> + .old = &counters->max,
> + },
> + {
> + .name = "oom",
> + .new = &new_counters.oom,
> + .old = &counters->oom,
> + },
> + {
> + .name = "oom_kill",
> + .new = &new_counters.oom_kill,
> + .old = &counters->oom_kill,
> + },
> + {
> + .name = "oom_group_kill",
> + .new = &new_counters.oom_group_kill,
> + .old = &counters->oom_group_kill,
> + },
> + };
> +
> + if (!fp) {
> + warn("Failed to open memcg events file %s", events->path);
> + return -EBADF;
> + }
> +
> + /* Read new values for memcg counters */
> + for (i = 0; i < ARRAY_SIZE(map); ++i) {
> + ssize_t nread;
> +
> + errno = 0;
> + nread = getline(&line, &len, fp);
> + if (nread == -1) {
> + if (errno) {
> + warn("Failed to read line for counter %s",
> + map[i].name);
> + ret = -EIO;
> + goto exit;
> + }
> +
> + break;
> + }
> +
> + ret = get_memcg_counter(line, map[i].name, map[i].new);
> + if (ret) {
> + warnx("Failed to get counter value from line %s", line);
> + goto exit;
> + }
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(map); ++i) {
> + long diff;
> +
> + if (*map[i].new > *map[i].old) {
> + diff = *map[i].new - *map[i].old;
> +
> + if (show_diff)
> + printf("*** %ld MEMCG %s event%s, "
> + "change counter %ld => %ld\n",
> + diff, map[i].name,
> + (diff == 1) ? "" : "s",
> + *map[i].old, *map[i].new);
> +
> + *map[i].old += diff;
> + any_new_events = true;
> + }
> + }
> +
> + if (show_diff && !any_new_events)
> + printf("*** No new untracked memcg events available\n");
> +
> +exit:
> + free(line);
> + fclose(fp);
> +
> + return ret;
> +}
> +
> +static void process_memcg_events(struct memcg_events *events,
> + struct inotify_event *event)
> +{
> + int ret;
> +
> + if (events->inotify_wd != event->wd) {
> + warnx("Unknown inotify event %d, should be %d", event->wd,
> + events->inotify_wd);
> + return;
> + }
> +
> + printf("Received event in %s:\n", events->path);
> +
> + if (!(event->mask & IN_MODIFY)) {
> + warnx("No IN_MODIFY event, skip it");
> + return;
> + }
> +
> + ret = read_memcg_events(events, /* show_diff = */true);
> + if (ret)
> + warnx("Can't read memcg events");
> +}
> +
> +static void monitor_events(struct memcg_events *events)
> +{
> + struct pollfd fds[1];
> + int ret;
> +
> + printf("Started monitoring memory events from '%s'...\n", events->path);
> +
> + fds[0].fd = events->inotify_fd;
> + fds[0].events = POLLIN;
> +
> + for (;;) {
> + ret = poll(fds, ARRAY_SIZE(fds), -1);
> + if (ret < 0 && errno != EAGAIN)
> + err(EXIT_FAILURE, "Can't poll memcg events (%d)", ret);
> +
> + if (fds[0].revents & POLLERR)
> + err(EXIT_FAILURE, "Got POLLERR during monitor events");
> +
> + if (fds[0].revents & POLLIN) {
> + struct inotify_event *event;
> + char buffer[INOTIFY_BUFFER_SIZE];
> + ssize_t length;
> +
> + length = read(fds[0].fd, buffer, INOTIFY_BUFFER_SIZE);
> + if (length <= 0)
> + continue;
> +
> + event = (struct inotify_event *)buffer;
> + while (INOTIFY_EVENT_OK(event, length)) {
> + process_memcg_events(events, event);
> + event = INOTIFY_EVENT_NEXT(event, length);
> + }
> + }
> + }
> +}
> +
> +static int initialize_memcg_events(struct memcg_events *events,
> + const char *cgroup)
> +{
> + int ret;
> +
> + memset(events, 0, sizeof(struct memcg_events));
> +
> + ret = snprintf(events->path, PATH_MAX,
> + "/sys/fs/cgroup/%s/memory.events", cgroup);
> + if (ret >= PATH_MAX) {
> + warnx("Path to cgroup memory.events is too long");
> + return -EMSGSIZE;
> + } else if (ret < 0) {
> + warn("Can't generate cgroup event full name");
> + return ret;
> + }
> +
> + ret = read_memcg_events(events, /* show_diff = */false);
> + if (ret) {
> + warnx("Failed to read initial memcg events state (%d)", ret);
> + return ret;
> + }
> +
> + events->inotify_fd = inotify_init();
> + if (events->inotify_fd < 0) {
> + warn("Failed to setup new inotify device");
> + return -EMFILE;
> + }
> +
> + events->inotify_wd = inotify_add_watch(events->inotify_fd,
> + events->path, IN_MODIFY);
> + if (events->inotify_wd < 0) {
> + warn("Couldn't add monitor in dir %s", events->path);
> + return -EIO;
> + }
> +
> + printf("Initialized MEMCG events with counters:\n");
> + print_memcg_counters(&events->counters);
> +
> + return 0;
> +}
> +
> +static void cleanup_memcg_events(struct memcg_events *events)
> +{
> + inotify_rm_watch(events->inotify_fd, events->inotify_wd);
> + close(events->inotify_fd);
> +}
> +
> +int main(int argc, const char **argv)
> +{
> + struct memcg_events events;
> + ssize_t ret;
> +
> + if (argc != 2)
> + errx(EXIT_FAILURE, "Usage: %s <cgroup>", argv[0]);
> +
> + ret = initialize_memcg_events(&events, argv[1]);
> + if (ret)
> + errx(EXIT_FAILURE, "Can't initialize memcg events (%zd)", ret);
> +
> + monitor_events(&events);
> +
> + cleanup_memcg_events(&events);
> +
> + printf("Exiting cgroup v2 event listener...\n");
> +
> + return EXIT_SUCCESS;
> +}
> --
> 2.36.0
>
--
Thank you,
Dmitry
