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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/[email protected] Signed-off-by: Dmitry Rokosov <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Muchun Song <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Shakeel Butt <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
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# SPDX-License-Identifier: GPL-2.0 | ||
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userprogs-always-y += cgroup_event_listener | ||
userprogs-always-y += cgroup_event_listener memcg_event_listener | ||
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userccflags += -I usr/include |
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// 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]> | ||
*/ | ||
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#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> | ||
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#define MEMCG_EVENTS "memory.events" | ||
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/* Size of buffer to use when reading inotify events */ | ||
#define INOTIFY_BUFFER_SIZE 8192 | ||
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#define INOTIFY_EVENT_NEXT(event, length) ({ \ | ||
(length) -= sizeof(*(event)) + (event)->len; \ | ||
(event)++; \ | ||
}) | ||
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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 { | ||
long low; | ||
long high; | ||
long max; | ||
long oom; | ||
long oom_kill; | ||
long oom_group_kill; | ||
}; | ||
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struct memcg_events { | ||
struct memcg_counters counters; | ||
char path[PATH_MAX]; | ||
int inotify_fd; | ||
int inotify_wd; | ||
}; | ||
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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); | ||
} | ||
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static int get_memcg_counter(char *line, const char *name, long *counter) | ||
{ | ||
size_t len = strlen(name); | ||
char *endptr; | ||
long tmp; | ||
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if (memcmp(line, name, len)) { | ||
warnx("Counter line %s has wrong name, %s is expected", | ||
line, name); | ||
return -EINVAL; | ||
} | ||
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/* skip the whitespace delimiter */ | ||
len += 1; | ||
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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; | ||
} | ||
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if (endptr == &line[len]) { | ||
warnx("Not digits were found in line %s", &line[len]); | ||
return -EINVAL; | ||
} | ||
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if (!(*endptr == '\0' || (*endptr == '\n' && *++endptr == '\0'))) { | ||
warnx("Further characters after number: %s", endptr); | ||
return -EINVAL; | ||
} | ||
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*counter = tmp; | ||
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return 0; | ||
} | ||
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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, | ||
}, | ||
}; | ||
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if (!fp) { | ||
warn("Failed to open memcg events file %s", events->path); | ||
return -EBADF; | ||
} | ||
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/* Read new values for memcg counters */ | ||
for (i = 0; i < ARRAY_SIZE(map); ++i) { | ||
ssize_t nread; | ||
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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; | ||
} | ||
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break; | ||
} | ||
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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; | ||
} | ||
} | ||
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for (i = 0; i < ARRAY_SIZE(map); ++i) { | ||
long diff; | ||
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if (*map[i].new > *map[i].old) { | ||
diff = *map[i].new - *map[i].old; | ||
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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); | ||
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*map[i].old += diff; | ||
any_new_events = true; | ||
} | ||
} | ||
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if (show_diff && !any_new_events) | ||
printf("*** No new untracked memcg events available\n"); | ||
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exit: | ||
free(line); | ||
fclose(fp); | ||
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return ret; | ||
} | ||
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static void process_memcg_events(struct memcg_events *events, | ||
struct inotify_event *event) | ||
{ | ||
int ret; | ||
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if (events->inotify_wd != event->wd) { | ||
warnx("Unknown inotify event %d, should be %d", event->wd, | ||
events->inotify_wd); | ||
return; | ||
} | ||
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printf("Received event in %s:\n", events->path); | ||
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if (!(event->mask & IN_MODIFY)) { | ||
warnx("No IN_MODIFY event, skip it"); | ||
return; | ||
} | ||
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ret = read_memcg_events(events, /* show_diff = */true); | ||
if (ret) | ||
warnx("Can't read memcg events"); | ||
} | ||
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static void monitor_events(struct memcg_events *events) | ||
{ | ||
struct pollfd fds[1]; | ||
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; | ||
fds[0].events = POLLIN; | ||
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for (;;) { | ||
ret = poll(fds, ARRAY_SIZE(fds), -1); | ||
if (ret < 0 && errno != EAGAIN) | ||
err(EXIT_FAILURE, "Can't poll memcg events (%d)", ret); | ||
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if (fds[0].revents & POLLERR) | ||
err(EXIT_FAILURE, "Got POLLERR during monitor events"); | ||
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if (fds[0].revents & POLLIN) { | ||
struct inotify_event *event; | ||
char buffer[INOTIFY_BUFFER_SIZE]; | ||
ssize_t length; | ||
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length = read(fds[0].fd, buffer, INOTIFY_BUFFER_SIZE); | ||
if (length <= 0) | ||
continue; | ||
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event = (struct inotify_event *)buffer; | ||
while (INOTIFY_EVENT_OK(event, length)) { | ||
process_memcg_events(events, event); | ||
event = INOTIFY_EVENT_NEXT(event, length); | ||
} | ||
} | ||
} | ||
} | ||
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static int initialize_memcg_events(struct memcg_events *events, | ||
const char *cgroup) | ||
{ | ||
int ret; | ||
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memset(events, 0, sizeof(struct memcg_events)); | ||
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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; | ||
} | ||
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ret = read_memcg_events(events, /* show_diff = */false); | ||
if (ret) { | ||
warnx("Failed to read initial memcg events state (%d)", ret); | ||
return ret; | ||
} | ||
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events->inotify_fd = inotify_init(); | ||
if (events->inotify_fd < 0) { | ||
warn("Failed to setup new inotify device"); | ||
return -EMFILE; | ||
} | ||
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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; | ||
} | ||
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printf("Initialized MEMCG events with counters:\n"); | ||
print_memcg_counters(&events->counters); | ||
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return 0; | ||
} | ||
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static void cleanup_memcg_events(struct memcg_events *events) | ||
{ | ||
inotify_rm_watch(events->inotify_fd, events->inotify_wd); | ||
close(events->inotify_fd); | ||
} | ||
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int main(int argc, const char **argv) | ||
{ | ||
struct memcg_events events; | ||
ssize_t ret; | ||
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if (argc != 2) | ||
errx(EXIT_FAILURE, "Usage: %s <cgroup>", argv[0]); | ||
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ret = initialize_memcg_events(&events, argv[1]); | ||
if (ret) | ||
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; | ||
} |