Patch series "samples: introduce cgroup events listeners", v3.
To begin with, this patch series relocates the cgroup example code to the
samples/cgroup directory, which is the appropriate location for such code
snippets.
Furthermore, a new memcg events listener is introduced. This listener is
a simple yet effective tool for monitoring memory events and managing
counter changes during runtime.
Additionally, as per Andrew Morton's suggestion, a helpful reminder
comment is included in the memcontrol implementation. This comment serves
to ensure that the samples code is updated whenever new events are added.
This patch (of 3):
Move the cgroup_event_listener for cgroup v1 to the samples directory.
This suggestion was proposed by Andrew Morton during the discussion [1].
Link: https://lore.kernel.org/all/20231106140934.3f5d4960141562fe8da53906@linux-foundation.org/
Link: https://lkml.kernel.org/r/20231123071945.25811-1-ddrokosov@salutedevices.com
Link: https://lkml.kernel.org/r/20231123071945.25811-2-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>
S: Maintained
F: mm/memcontrol.c
F: mm/swap_cgroup.c
+F: samples/cgroup/*
F: tools/testing/selftests/cgroup/memcg_protection.m
F: tools/testing/selftests/cgroup/test_hugetlb_memcg.c
F: tools/testing/selftests/cgroup/test_kmem.c
Build a sample program which have explicitly leaks memory to test
kmemleak
+config SAMPLE_CGROUP
+ bool "Build cgroup sample code"
+ depends on CGROUPS && CC_CAN_LINK && HEADERS_INSTALL
+ help
+ Build samples that demonstrate the usage of the cgroup API.
+
source "samples/rust/Kconfig"
endif # SAMPLES
subdir-$(CONFIG_SAMPLE_AUXDISPLAY) += auxdisplay
subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs
+subdir-$(CONFIG_SAMPLE_CGROUP) += cgroup
obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/
obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/
obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fanotify/
--- /dev/null
+# SPDX-License-Identifier: GPL-2.0
+
+userprogs-always-y += cgroup_event_listener
+
+userccflags += -I usr/include
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * cgroup_event_listener.c - Simple listener of cgroup events
+ *
+ * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
+ */
+
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/eventfd.h>
+
+#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
+
+int main(int argc, char **argv)
+{
+ int efd = -1;
+ int cfd = -1;
+ int event_control = -1;
+ char event_control_path[PATH_MAX];
+ char line[LINE_MAX];
+ int ret;
+
+ if (argc != 3)
+ errx(1, "%s", USAGE_STR);
+
+ cfd = open(argv[1], O_RDONLY);
+ if (cfd == -1)
+ err(1, "Cannot open %s", argv[1]);
+
+ ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
+ dirname(argv[1]));
+ if (ret >= PATH_MAX)
+ errx(1, "Path to cgroup.event_control is too long");
+
+ event_control = open(event_control_path, O_WRONLY);
+ if (event_control == -1)
+ err(1, "Cannot open %s", event_control_path);
+
+ efd = eventfd(0, 0);
+ if (efd == -1)
+ err(1, "eventfd() failed");
+
+ ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
+ if (ret >= LINE_MAX)
+ errx(1, "Arguments string is too long");
+
+ ret = write(event_control, line, strlen(line) + 1);
+ if (ret == -1)
+ err(1, "Cannot write to cgroup.event_control");
+
+ while (1) {
+ uint64_t result;
+
+ ret = read(efd, &result, sizeof(result));
+ if (ret == -1) {
+ if (errno == EINTR)
+ continue;
+ err(1, "Cannot read from eventfd");
+ }
+ assert(ret == sizeof(result));
+
+ ret = access(event_control_path, W_OK);
+ if ((ret == -1) && (errno == ENOENT)) {
+ puts("The cgroup seems to have removed.");
+ break;
+ }
+
+ if (ret == -1)
+ err(1, "cgroup.event_control is not accessible any more");
+
+ printf("%s %s: crossed\n", argv[1], argv[2]);
+ }
+
+ return 0;
+}
+++ /dev/null
-# SPDX-License-Identifier: GPL-2.0
-# Makefile for cgroup tools
-
-CFLAGS = -Wall -Wextra
-
-all: cgroup_event_listener
-%: %.c
- $(CC) $(CFLAGS) -o $@ $^
-
-clean:
- $(RM) cgroup_event_listener
+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0
-/*
- * cgroup_event_listener.c - Simple listener of cgroup events
- *
- * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
- */
-
-#include <assert.h>
-#include <err.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <libgen.h>
-#include <limits.h>
-#include <stdio.h>
-#include <string.h>
-#include <unistd.h>
-
-#include <sys/eventfd.h>
-
-#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
-
-int main(int argc, char **argv)
-{
- int efd = -1;
- int cfd = -1;
- int event_control = -1;
- char event_control_path[PATH_MAX];
- char line[LINE_MAX];
- int ret;
-
- if (argc != 3)
- errx(1, "%s", USAGE_STR);
-
- cfd = open(argv[1], O_RDONLY);
- if (cfd == -1)
- err(1, "Cannot open %s", argv[1]);
-
- ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
- dirname(argv[1]));
- if (ret >= PATH_MAX)
- errx(1, "Path to cgroup.event_control is too long");
-
- event_control = open(event_control_path, O_WRONLY);
- if (event_control == -1)
- err(1, "Cannot open %s", event_control_path);
-
- efd = eventfd(0, 0);
- if (efd == -1)
- err(1, "eventfd() failed");
-
- ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
- if (ret >= LINE_MAX)
- errx(1, "Arguments string is too long");
-
- ret = write(event_control, line, strlen(line) + 1);
- if (ret == -1)
- err(1, "Cannot write to cgroup.event_control");
-
- while (1) {
- uint64_t result;
-
- ret = read(efd, &result, sizeof(result));
- if (ret == -1) {
- if (errno == EINTR)
- continue;
- err(1, "Cannot read from eventfd");
- }
- assert(ret == sizeof(result));
-
- ret = access(event_control_path, W_OK);
- if ((ret == -1) && (errno == ENOENT)) {
- puts("The cgroup seems to have removed.");
- break;
- }
-
- if (ret == -1)
- err(1, "cgroup.event_control is not accessible any more");
-
- printf("%s %s: crossed\n", argv[1], argv[2]);
- }
-
- return 0;
-}
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