[LTP] [PATCH v2 5/5] cgroup: Add memcontrol02
Richard Palethorpe
rpalethorpe@suse.com
Thu Dec 30 11:37:18 CET 2021
This test appears to compare the overall "current" counter with anon
and file (page cache) memory counters. The file test assumes much more
memory will be consumed by the page cache. This is certainly true on
XFS and BTRFS where little or no memory outside the page cache is
used. However on ext4, ntfs and especially exfat, we can see more
memory being used.
This seems to be related to fs/buffer.c and buffer_head usage. exfat
in particular allocates a lot of memory. This is possibly due to the
buffer_head being allocated in cont_write_begin:
Children Self Samples bytes_alloc Parent symbol
........ ........ ............ .................. .................
97.66% 97.66% 102401 168 exfat_write_begin
|
---0xf7eec549
entry_SYSENTER_compat_after_hwframe
do_fast_syscall_32
__noinstr_text_start
ksys_write
vfs_write
new_sync_write
generic_file_write_iter
__generic_file_write_iter
generic_perform_write
exfat_write_begin
cont_write_begin
__block_write_begin_int
create_page_buffers
create_empty_buffers
alloc_page_buffers
alloc_buffer_head
kmem_cache_alloc
kmem_cache_alloc
0.20% 0.20% 205 584 exfat_write_begin
0.06% 0.06% 64 168 exfat_fill_super
0.05% 0.05% 49 256 exfat_fill_super
0.00% 0.00% 4 584 exfat_fill_super
0.00% 0.00% 1 256 exfat_create
0.00% 0.00% 1 1528 exfat_create
0.00% 0.00% 1 1528 exfat_fill_super
0.00% 0.00% 1 312 exfat_fill_super
We can see (using slub_debug=U,buffer_head) that these buffer_head
objects are not freed until the file is unlinked:
Outputting '/sys/kernel/debug/slab/buffer_head/alloc_traces' ...
102480 alloc_buffer_head+0x1b/0x90 age=0/268/2629529 pid=248-430 cpus=0,2
Outputting '/sys/kernel/debug/slab/buffer_head/free_traces' ...
102400 <not-available> age=4297543659 pid=0 cpus=0
80 free_buffer_head+0x21/0x60 age=147/266217/2629538 pid=337-427 cpus=1-2
ext4 and ntfs also use some of the "buffer" code, but don't seem to
allocate quite as much. Although ext4 begins to fail when slub debug
is enabled due to the extra memory debugging uses.
In any case, it appears that the CGroup code is correct, so I have
increased the error margin when exfat or ext234 is detected.
Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
runtest/controllers | 1 +
testcases/kernel/controllers/memcg/.gitignore | 1 +
.../kernel/controllers/memcg/memcontrol02.c | 182 ++++++++++++++++++
3 files changed, 184 insertions(+)
create mode 100644 testcases/kernel/controllers/memcg/memcontrol02.c
diff --git a/runtest/controllers b/runtest/controllers
index 2b41a94d3..09e0107e4 100644
--- a/runtest/controllers
+++ b/runtest/controllers
@@ -18,6 +18,7 @@ memcg_control memcg_control_test.sh
# kselftest ports
memcontrol01 memcontrol01
+memcontrol02 memcontrol02
cgroup_fj_function_debug cgroup_fj_function.sh debug
cgroup_fj_function_cpuset cgroup_fj_function.sh cpuset
diff --git a/testcases/kernel/controllers/memcg/.gitignore b/testcases/kernel/controllers/memcg/.gitignore
index c3565f85c..f7de40d53 100644
--- a/testcases/kernel/controllers/memcg/.gitignore
+++ b/testcases/kernel/controllers/memcg/.gitignore
@@ -6,3 +6,4 @@
/regression/memcg_test_4
/stress/memcg_process_stress
memcontrol01
+memcontrol02
diff --git a/testcases/kernel/controllers/memcg/memcontrol02.c b/testcases/kernel/controllers/memcg/memcontrol02.c
new file mode 100644
index 000000000..a6d2f7268
--- /dev/null
+++ b/testcases/kernel/controllers/memcg/memcontrol02.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+/*\
+ *
+ * [Description]
+ *
+ * Conversion of second kself test in cgroup/test_memcontrol.c.
+ *
+ * Original description:
+ * "This test creates a memory cgroup, allocates some anonymous memory
+ * and some pagecache and check memory.current and some memory.stat
+ * values."
+ *
+ * Note that the V1 rss and cache counters were renamed to anon and
+ * file in V2. Besides error reporting, this test differs from the
+ * kselftest in the following ways:
+ *
+ * . It supports V1.
+ * . It writes instead of reads to fill the page cache. Because no
+ * pages were allocated on tmpfs.
+ * . It runs on most filesystems available
+ * . On EXFAT and extN we change the margine of error between all and file
+ * memory to 50%. Because these allocate non-page-cache memory during writes.
+ */
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "tst_test.h"
+#include "tst_cgroup.h"
+
+#define TMPDIR "mntdir"
+#define MB(x) (x << 20)
+
+static size_t page_size;
+static const struct tst_cgroup_group *cg_test;
+static int is_v1_memcg;
+static struct tst_cgroup_group *cg_child;
+static int fd;
+static int file_to_all_error = 10;
+
+/*
+ * Checks if two given values differ by less than err% of their sum.
+ */
+static inline int values_close(const ssize_t a,
+ const ssize_t b,
+ const ssize_t err)
+{
+ return labs(a - b) <= (a + b) / 100 * err;
+}
+
+static void alloc_anon_50M_check(void)
+{
+ const ssize_t size = MB(50);
+ char *buf, *ptr;
+ ssize_t anon, current;
+ const char *const anon_key_fmt = is_v1_memcg ? "rss %zd" : "anon %zd";
+
+ buf = SAFE_MALLOC(size);
+ for (ptr = buf; ptr < buf + size; ptr += page_size)
+ *ptr = 0;
+
+ SAFE_CGROUP_SCANF(cg_child, "memory.current", "%zd", ¤t);
+ TST_EXP_EXPR(current >= size,
+ "(memory.current=%zd) >= (size=%zd)", current, size);
+
+ SAFE_CGROUP_LINES_SCANF(cg_child, "memory.stat", anon_key_fmt, &anon);
+
+ TST_EXP_EXPR(anon > 0, "(memory.stat.anon=%zd) > 0", anon);
+ TST_EXP_EXPR(values_close(size, current, 3),
+ "(size=%zd) ~= (memory.stat.anon=%zd)", size, current);
+ TST_EXP_EXPR(values_close(anon, current, 3),
+ "(memory.current=%zd) ~= (memory.stat.anon=%zd)",
+ current, anon);
+}
+
+static void alloc_pagecache(const int fd, size_t size)
+{
+ char buf[BUFSIZ];
+ size_t i;
+
+ for (i = 0; i < size; i += sizeof(buf))
+ SAFE_WRITE(1, fd, buf, sizeof(buf));
+}
+
+static void alloc_pagecache_50M_check(void)
+{
+ const size_t size = MB(50);
+ size_t current, file;
+ const char *const file_key_fmt = is_v1_memcg ? "cache %zd" : "file %zd";
+
+ TEST(open(TMPDIR"/tmpfile", O_RDWR | O_CREAT));
+
+ if (TST_RET < 0) {
+ if (TST_ERR == EOPNOTSUPP)
+ tst_brk(TCONF, "O_TMPFILE not supported by FS");
+
+ tst_brk(TBROK | TTERRNO,
+ "open(%s, O_TMPFILE | O_RDWR | O_EXCL", TMPDIR"/.");
+ }
+ fd = TST_RET;
+
+ SAFE_CGROUP_SCANF(cg_child, "memory.current", "%zu", ¤t);
+ tst_res(TINFO, "Created temp file: memory.current=%zu", current);
+
+ alloc_pagecache(fd, size);
+
+ SAFE_CGROUP_SCANF(cg_child, "memory.current", "%zu", ¤t);
+ TST_EXP_EXPR(current >= size,
+ "(memory.current=%zu) >= (size=%zu)", current, size);
+
+ SAFE_CGROUP_LINES_SCANF(cg_child, "memory.stat", file_key_fmt, &file);
+ TST_EXP_EXPR(file > 0, "(memory.stat.file=%zd) > 0", file);
+
+ TST_EXP_EXPR(values_close(file, current, file_to_all_error),
+ "(memory.current=%zd) ~= (memory.stat.file=%zd)",
+ current, file);
+
+ SAFE_CLOSE(fd);
+}
+
+static void test_memcg_current(unsigned int n)
+{
+ size_t current;
+
+ cg_child = tst_cgroup_group_mk(cg_test, "child");
+ SAFE_CGROUP_SCANF(cg_child, "memory.current", "%zu", ¤t);
+ TST_EXP_EXPR(current == 0, "(current=%zu) == 0", current);
+
+ if (!SAFE_FORK()) {
+ SAFE_CGROUP_PRINTF(cg_child, "cgroup.procs", "%d", getpid());
+
+ SAFE_CGROUP_SCANF(cg_child, "memory.current", "%zu", ¤t);
+ tst_res(TINFO, "Added proc to memcg: memory.current=%zu",
+ current);
+
+ if (!n)
+ alloc_anon_50M_check();
+ else
+ alloc_pagecache_50M_check();
+ } else {
+ tst_reap_children();
+ cg_child = tst_cgroup_group_rm(cg_child);
+ }
+}
+
+static void setup(void)
+{
+ page_size = SAFE_SYSCONF(_SC_PAGESIZE);
+
+ tst_cgroup_require("memory", NULL);
+ cg_test = tst_cgroup_get_test_group();
+
+ is_v1_memcg = TST_CGROUP_VER(cg_test, "memory") == TST_CGROUP_V1;
+
+ switch (tst_fs_type(TMPDIR)) {
+ case TST_EXFAT_MAGIC:
+ case TST_EXT234_MAGIC:
+ file_to_all_error = 50;
+ break;
+ }
+}
+
+static void cleanup(void)
+{
+ if (cg_child)
+ cg_child = tst_cgroup_group_rm(cg_child);
+
+ tst_cgroup_cleanup();
+}
+
+static struct tst_test test = {
+ .setup = setup,
+ .cleanup = cleanup,
+ .tcnt = 2,
+ .test = test_memcg_current,
+ .mount_device = 1,
+ .dev_min_size = 256,
+ .mntpoint = TMPDIR,
+ .all_filesystems = 1,
+ .forks_child = 1,
+};
--
2.34.0
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