// SPDX-License-Identifier: GPL-2.0
/*
* memcg_event_listener.c - Simple listener of memcg memory.events
*
* Copyright (c) 2023, SaluteDevices. All Rights Reserved.
*
* Author: Dmitry Rokosov <[email protected]>
*/
#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 memcg event listener...\n");
return EXIT_SUCCESS;
}
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