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samples/cgroup: introduce memcg memory.events listener
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/memcg_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 memcg event listener... ===== Link: https://lkml.kernel.org/r/20231123071945.25811-3-ddrokosov@salutedevices.com Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dmitry Rokosov
Andrew Morton
parent
60433a9d03
commit
becf652960
@ -1,5 +1,5 @@
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# SPDX-License-Identifier: GPL-2.0
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userprogs-always-y += cgroup_event_listener
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userprogs-always-y += cgroup_event_listener memcg_event_listener
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userccflags += -I usr/include
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330
samples/cgroup/memcg_event_listener.c
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330
samples/cgroup/memcg_event_listener.c
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@ -0,0 +1,330 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* memcg_event_listener.c - Simple listener of memcg memory.events
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*
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* Copyright (c) 2023, SaluteDevices. All Rights Reserved.
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*
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* Author: Dmitry Rokosov <ddrokosov@salutedevices.com>
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*/
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#include <err.h>
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#include <errno.h>
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#include <limits.h>
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#include <poll.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/inotify.h>
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#include <unistd.h>
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#define MEMCG_EVENTS "memory.events"
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/* Size of buffer to use when reading inotify events */
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#define INOTIFY_BUFFER_SIZE 8192
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#define INOTIFY_EVENT_NEXT(event, length) ({ \
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(length) -= sizeof(*(event)) + (event)->len; \
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(event)++; \
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})
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#define INOTIFY_EVENT_OK(event, length) ((length) >= (ssize_t)sizeof(*(event)))
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#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
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struct memcg_counters {
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long low;
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long high;
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long max;
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long oom;
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long oom_kill;
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long oom_group_kill;
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};
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struct memcg_events {
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struct memcg_counters counters;
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char path[PATH_MAX];
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int inotify_fd;
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int inotify_wd;
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};
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static void print_memcg_counters(const struct memcg_counters *counters)
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{
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printf("MEMCG events:\n");
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printf("\tlow: %ld\n", counters->low);
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printf("\thigh: %ld\n", counters->high);
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printf("\tmax: %ld\n", counters->max);
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printf("\toom: %ld\n", counters->oom);
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printf("\toom_kill: %ld\n", counters->oom_kill);
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printf("\toom_group_kill: %ld\n", counters->oom_group_kill);
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}
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static int get_memcg_counter(char *line, const char *name, long *counter)
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{
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size_t len = strlen(name);
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char *endptr;
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long tmp;
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if (memcmp(line, name, len)) {
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warnx("Counter line %s has wrong name, %s is expected",
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line, name);
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return -EINVAL;
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}
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/* skip the whitespace delimiter */
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len += 1;
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errno = 0;
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tmp = strtol(&line[len], &endptr, 10);
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if (((tmp == LONG_MAX || tmp == LONG_MIN) && errno == ERANGE) ||
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(errno && !tmp)) {
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warnx("Failed to parse: %s", &line[len]);
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return -ERANGE;
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}
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if (endptr == &line[len]) {
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warnx("Not digits were found in line %s", &line[len]);
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return -EINVAL;
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}
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if (!(*endptr == '\0' || (*endptr == '\n' && *++endptr == '\0'))) {
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warnx("Further characters after number: %s", endptr);
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return -EINVAL;
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}
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*counter = tmp;
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return 0;
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}
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static int read_memcg_events(struct memcg_events *events, bool show_diff)
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{
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FILE *fp = fopen(events->path, "re");
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size_t i;
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int ret = 0;
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bool any_new_events = false;
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char *line = NULL;
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size_t len = 0;
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struct memcg_counters new_counters;
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struct memcg_counters *counters = &events->counters;
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struct {
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const char *name;
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long *new;
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long *old;
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} map[] = {
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{
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.name = "low",
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.new = &new_counters.low,
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.old = &counters->low,
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},
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{
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.name = "high",
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.new = &new_counters.high,
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.old = &counters->high,
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},
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{
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.name = "max",
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.new = &new_counters.max,
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.old = &counters->max,
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},
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{
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.name = "oom",
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.new = &new_counters.oom,
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.old = &counters->oom,
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},
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{
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.name = "oom_kill",
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.new = &new_counters.oom_kill,
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.old = &counters->oom_kill,
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},
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{
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.name = "oom_group_kill",
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.new = &new_counters.oom_group_kill,
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.old = &counters->oom_group_kill,
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},
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};
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if (!fp) {
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warn("Failed to open memcg events file %s", events->path);
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return -EBADF;
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}
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/* Read new values for memcg counters */
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for (i = 0; i < ARRAY_SIZE(map); ++i) {
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ssize_t nread;
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errno = 0;
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nread = getline(&line, &len, fp);
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if (nread == -1) {
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if (errno) {
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warn("Failed to read line for counter %s",
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map[i].name);
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ret = -EIO;
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goto exit;
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}
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break;
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}
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ret = get_memcg_counter(line, map[i].name, map[i].new);
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if (ret) {
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warnx("Failed to get counter value from line %s", line);
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goto exit;
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}
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}
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for (i = 0; i < ARRAY_SIZE(map); ++i) {
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long diff;
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if (*map[i].new > *map[i].old) {
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diff = *map[i].new - *map[i].old;
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if (show_diff)
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printf("*** %ld MEMCG %s event%s, "
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"change counter %ld => %ld\n",
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diff, map[i].name,
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(diff == 1) ? "" : "s",
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*map[i].old, *map[i].new);
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*map[i].old += diff;
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any_new_events = true;
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}
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}
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if (show_diff && !any_new_events)
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printf("*** No new untracked memcg events available\n");
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exit:
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free(line);
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fclose(fp);
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return ret;
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}
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static void process_memcg_events(struct memcg_events *events,
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struct inotify_event *event)
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{
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int ret;
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if (events->inotify_wd != event->wd) {
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warnx("Unknown inotify event %d, should be %d", event->wd,
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events->inotify_wd);
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return;
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}
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printf("Received event in %s:\n", events->path);
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if (!(event->mask & IN_MODIFY)) {
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warnx("No IN_MODIFY event, skip it");
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return;
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}
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ret = read_memcg_events(events, /* show_diff = */true);
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if (ret)
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warnx("Can't read memcg events");
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}
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static void monitor_events(struct memcg_events *events)
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{
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struct pollfd fds[1];
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int ret;
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printf("Started monitoring memory events from '%s'...\n", events->path);
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fds[0].fd = events->inotify_fd;
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fds[0].events = POLLIN;
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for (;;) {
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ret = poll(fds, ARRAY_SIZE(fds), -1);
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if (ret < 0 && errno != EAGAIN)
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err(EXIT_FAILURE, "Can't poll memcg events (%d)", ret);
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if (fds[0].revents & POLLERR)
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err(EXIT_FAILURE, "Got POLLERR during monitor events");
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if (fds[0].revents & POLLIN) {
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struct inotify_event *event;
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char buffer[INOTIFY_BUFFER_SIZE];
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ssize_t length;
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length = read(fds[0].fd, buffer, INOTIFY_BUFFER_SIZE);
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if (length <= 0)
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continue;
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event = (struct inotify_event *)buffer;
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while (INOTIFY_EVENT_OK(event, length)) {
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process_memcg_events(events, event);
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event = INOTIFY_EVENT_NEXT(event, length);
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}
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}
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}
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}
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static int initialize_memcg_events(struct memcg_events *events,
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const char *cgroup)
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{
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int ret;
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memset(events, 0, sizeof(struct memcg_events));
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ret = snprintf(events->path, PATH_MAX,
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"/sys/fs/cgroup/%s/memory.events", cgroup);
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if (ret >= PATH_MAX) {
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warnx("Path to cgroup memory.events is too long");
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return -EMSGSIZE;
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} else if (ret < 0) {
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warn("Can't generate cgroup event full name");
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return ret;
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}
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ret = read_memcg_events(events, /* show_diff = */false);
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if (ret) {
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warnx("Failed to read initial memcg events state (%d)", ret);
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return ret;
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}
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events->inotify_fd = inotify_init();
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if (events->inotify_fd < 0) {
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warn("Failed to setup new inotify device");
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return -EMFILE;
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}
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events->inotify_wd = inotify_add_watch(events->inotify_fd,
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events->path, IN_MODIFY);
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if (events->inotify_wd < 0) {
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warn("Couldn't add monitor in dir %s", events->path);
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return -EIO;
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}
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printf("Initialized MEMCG events with counters:\n");
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print_memcg_counters(&events->counters);
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return 0;
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}
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static void cleanup_memcg_events(struct memcg_events *events)
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{
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inotify_rm_watch(events->inotify_fd, events->inotify_wd);
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close(events->inotify_fd);
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}
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int main(int argc, const char **argv)
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{
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struct memcg_events events;
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ssize_t ret;
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if (argc != 2)
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errx(EXIT_FAILURE, "Usage: %s <cgroup>", argv[0]);
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ret = initialize_memcg_events(&events, argv[1]);
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if (ret)
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errx(EXIT_FAILURE, "Can't initialize memcg events (%zd)", ret);
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monitor_events(&events);
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cleanup_memcg_events(&events);
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printf("Exiting memcg event listener...\n");
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return EXIT_SUCCESS;
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}
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