[LTP] [PATCH v7] memcg/memcontrol05: add cgroup v2 task migration charge accounting test

[LTP] [PATCH v7] memcg/memcontrol05: add cgroup v2 task migration charge accounting test

[Pavithra]

Verify that in cgroup v2, memory charges remain pinned to the cgroup
that allocated them when a task migrates, and that new allocations after
migration are charged to the destination cgroup.

Signed-off-by: Pavithra <pavrampu@linux.ibm.com>
---
v6 -> v7:
- Replace named checkpoint enum with single index 0
- Collapse wake/wait pairs into TST_CHECKPOINT_WAKE_AND_WAIT(0)
- Drop worker_stage tracking
- Replace manual pass/fail blocks with TST_EXP_LE_LU()
- Remove MB(4) factor from migration charge check
- Kill worker with SAFE_KILL/SAFE_WAITPID instead of checkpoint-based exit handshake
link to v6: https://lore.kernel.org/ltp/20260817155701.943752-1-pavrampu@linux.ibm.com/
---
 runtest/controllers                           |   1 +
 testcases/kernel/controllers/memcg/.gitignore |   1 +
 .../kernel/controllers/memcg/memcontrol05.c   | 160 ++++++++++++++++++
 3 files changed, 162 insertions(+)
 create mode 100644 testcases/kernel/controllers/memcg/memcontrol05.c

diff --git a/runtest/controllers b/runtest/controllers
index 93c52c439..a9050ef0e 100644
--- a/runtest/controllers
+++ b/runtest/controllers
@@ -24,6 +24,7 @@ memcontrol01 memcontrol01
 memcontrol02 memcontrol02
 memcontrol03 memcontrol03
 memcontrol04 memcontrol04
+memcontrol05 memcontrol05
 
 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 3883cede6..8b9f6005c 100644
--- a/testcases/kernel/controllers/memcg/.gitignore
+++ b/testcases/kernel/controllers/memcg/.gitignore
@@ -9,3 +9,4 @@ memcontrol01
 memcontrol02
 memcontrol03
 memcontrol04
+memcontrol05
diff --git a/testcases/kernel/controllers/memcg/memcontrol05.c b/testcases/kernel/controllers/memcg/memcontrol05.c
new file mode 100644
index 000000000..d452039e6
--- /dev/null
+++ b/testcases/kernel/controllers/memcg/memcontrol05.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2026 IBM
+ * Author : Pavithra <pavrampu@linux.ibm.com>
+ */
+
+/*\
+ * Origin: ``testcases/kernel/controllers/memctl/memctl_testplan.txt``
+ * Verify memory controller charge accounting during task migration.
+ *
+ * Two child cgroups (``group_a``, ``group_b``) are created under the test cgroup.
+ * A worker process is placed in ``group_a`` and allocates a known amount of
+ * anonymous memory, touching every page to ensure physical allocation.
+ * Root is required to create cgroup subdirectories and to write a PID
+ * into ``cgroup.procs`` to migrate the worker between cgroups.
+ *
+ * Test 1 - No charge transfer on migration:
+ *   The worker is migrated to ``group_b`` by writing its PID to
+ *   ``group_b/cgroup.procs``. In cgroup v2 memory charges are never
+ *   transferred on task migration; they remain pinned to the cgroup
+ *   that allocated them. ``group_b/memory.current`` must not increase
+ *   beyond its baseline after the migration.
+ *
+ * Test 2 - New allocations charged to destination cgroup:
+ *   After migration the worker allocates an additional chunk of memory.
+ *   This new allocation must be charged to ``group_b``, so
+ *   ``group_b/memory.current`` must increase from the post-migration
+ *   baseline.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include "tst_test.h"
+#include "memcontrol_common.h"
+
+#define ALLOC_SIZE	MB(60)
+#define ALLOC_SIZE2	MB(20)
+#define MIN_MEM_AVAIL	128
+
+static struct tst_cg_group *group_a;
+static struct tst_cg_group *group_b;
+static pid_t worker_pid;
+
+static void touch_pages(char *buf, size_t size)
+{
+	size_t i;
+
+	for (i = 0; i < size; i += getpagesize())
+		buf[i] = 1;
+}
+
+static void worker(void)
+{
+	char *buf1, *buf2;
+
+	SAFE_CG_PRINTF(group_a, "cgroup.procs", "%d", getpid());
+
+	buf1 = SAFE_MMAP(NULL, ALLOC_SIZE, PROT_READ | PROT_WRITE,
+			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	touch_pages(buf1, ALLOC_SIZE);
+
+	TST_CHECKPOINT_WAKE_AND_WAIT(0);
+
+	buf2 = SAFE_MMAP(NULL, ALLOC_SIZE2, PROT_READ | PROT_WRITE,
+			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	touch_pages(buf2, ALLOC_SIZE2);
+
+	TST_CHECKPOINT_WAKE(0);
+
+	pause();
+}
+
+static void test_memcg_task_migration(void)
+{
+	long baseline_b, after_migrate, after_migrate_a, after_alloc2, current_a;
+
+	worker_pid = 0;
+
+	group_a = tst_cg_group_mk(tst_cg, "group_a");
+	group_b = tst_cg_group_mk(tst_cg, "group_b");
+
+	if (SAFE_CG_HAS(tst_cg, "memory.swap.max")) {
+		SAFE_CG_PRINT(group_a, "memory.swap.max", "0");
+		SAFE_CG_PRINT(group_b, "memory.swap.max", "0");
+	}
+
+	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &baseline_b);
+	tst_res(TINFO, "group_b baseline memory.current=%ld", baseline_b);
+
+	worker_pid = SAFE_FORK();
+	if (!worker_pid) {
+		worker();
+		exit(0);
+	}
+
+	TST_CHECKPOINT_WAIT(0);
+
+	SAFE_CG_SCANF(group_a, "memory.current", "%ld", &current_a);
+	TST_EXP_LE_LU(ALLOC_SIZE, current_a);
+
+	SAFE_CG_PRINTF(group_b, "cgroup.procs", "%d", worker_pid);
+	tst_res(TINFO, "Migrated worker PID %d to group_b", worker_pid);
+
+	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &after_migrate);
+	tst_res(TINFO,
+		"group_b memory.current=%ld after migration (baseline=%ld)",
+		after_migrate, baseline_b);
+
+	TST_EXP_LE_LU(after_migrate, baseline_b);
+
+	SAFE_CG_SCANF(group_a, "memory.current", "%ld", &after_migrate_a);
+	tst_res(TINFO, "group_a memory.current=%ld after migration", after_migrate_a);
+	TST_EXP_EXPR(after_migrate_a >= (long)ALLOC_SIZE,
+		     "group_a memory.current (%ld) still holds pre-migration charges (>= ALLOC_SIZE %ld)",
+		     after_migrate_a, (long)ALLOC_SIZE);
+
+	TST_CHECKPOINT_WAKE_AND_WAIT(0);
+
+	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &after_alloc2);
+	tst_res(TINFO, "group_b memory.current=%ld after second alloc (baseline=%ld)",
+		after_alloc2, after_migrate);
+
+	TST_EXP_EXPR(after_alloc2 >= after_migrate + (long)ALLOC_SIZE2,
+		     "group_b memory.current (%ld) increased by >= ALLOC_SIZE2 (%ld)",
+		     after_alloc2, (long)ALLOC_SIZE2);
+
+	SAFE_KILL(worker_pid, SIGKILL);
+	SAFE_WAITPID(worker_pid, NULL, 0);
+	worker_pid = 0;
+
+	group_a = tst_cg_group_rm(group_a);
+	group_b = tst_cg_group_rm(group_b);
+}
+
+static void cleanup(void)
+{
+	if (worker_pid) {
+		SAFE_KILL(worker_pid, SIGKILL);
+		SAFE_WAITPID(worker_pid, NULL, 0);
+	}
+
+	if (group_a)
+		group_a = tst_cg_group_rm(group_a);
+	if (group_b)
+		group_b = tst_cg_group_rm(group_b);
+}
+
+static struct tst_test test = {
+	.test_all	= test_memcg_task_migration,
+	.cleanup	= cleanup,
+	.forks_child	= 1,
+	.needs_root	= 1,
+	.needs_checkpoints = 1,
+	.needs_cgroup_ver  = TST_CG_V2,
+	.needs_cgroup_ctrls = (const char *const []){ "memory", NULL },
+	.min_mem_avail	= MIN_MEM_AVAIL,
+};
-- 
2.55.0


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] memcg/memcontrol05: add cgroup v2 task migration charge accounting test

[linuxtestproject.agent]

Hi Pavithra,

On Sun, 30 Aug 2026, Pavithra wrote:
> memcg/memcontrol05: add cgroup v2 task migration charge accounting test

Verdict - Reviewed

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v7] memcg/memcontrol05: add cgroup v2 task migration charge accounting test

[Cyril Hrubis]

Hi!
> Verify that in cgroup v2, memory charges remain pinned to the cgroup
> that allocated them when a task migrates, and that new allocations after
> migration are charged to the destination cgroup.
> 
> Signed-off-by: Pavithra <pavrampu@linux.ibm.com>
> ---
> v6 -> v7:
> - Replace named checkpoint enum with single index 0
> - Collapse wake/wait pairs into TST_CHECKPOINT_WAKE_AND_WAIT(0)
> - Drop worker_stage tracking
> - Replace manual pass/fail blocks with TST_EXP_LE_LU()
> - Remove MB(4) factor from migration charge check
> - Kill worker with SAFE_KILL/SAFE_WAITPID instead of checkpoint-based exit handshake
> link to v6: https://lore.kernel.org/ltp/20260817155701.943752-1-pavrampu@linux.ibm.com/
> ---
>  runtest/controllers                           |   1 +
>  testcases/kernel/controllers/memcg/.gitignore |   1 +
>  .../kernel/controllers/memcg/memcontrol05.c   | 160 ++++++++++++++++++
>  3 files changed, 162 insertions(+)
>  create mode 100644 testcases/kernel/controllers/memcg/memcontrol05.c
> 
> diff --git a/runtest/controllers b/runtest/controllers
> index 93c52c439..a9050ef0e 100644
> --- a/runtest/controllers
> +++ b/runtest/controllers
> @@ -24,6 +24,7 @@ memcontrol01 memcontrol01
>  memcontrol02 memcontrol02
>  memcontrol03 memcontrol03
>  memcontrol04 memcontrol04
> +memcontrol05 memcontrol05
>  
>  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 3883cede6..8b9f6005c 100644
> --- a/testcases/kernel/controllers/memcg/.gitignore
> +++ b/testcases/kernel/controllers/memcg/.gitignore
> @@ -9,3 +9,4 @@ memcontrol01
>  memcontrol02
>  memcontrol03
>  memcontrol04
> +memcontrol05
> diff --git a/testcases/kernel/controllers/memcg/memcontrol05.c b/testcases/kernel/controllers/memcg/memcontrol05.c
> new file mode 100644
> index 000000000..d452039e6
> --- /dev/null
> +++ b/testcases/kernel/controllers/memcg/memcontrol05.c
> @@ -0,0 +1,160 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2026 IBM
> + * Author : Pavithra <pavrampu@linux.ibm.com>
> + */
> +
> +/*\
> + * Origin: ``testcases/kernel/controllers/memctl/memctl_testplan.txt``
> + * Verify memory controller charge accounting during task migration.
> + *
> + * Two child cgroups (``group_a``, ``group_b``) are created under the test cgroup.
> + * A worker process is placed in ``group_a`` and allocates a known amount of
> + * anonymous memory, touching every page to ensure physical allocation.
> + * Root is required to create cgroup subdirectories and to write a PID
> + * into ``cgroup.procs`` to migrate the worker between cgroups.
> + *
> + * Test 1 - No charge transfer on migration:
> + *   The worker is migrated to ``group_b`` by writing its PID to
> + *   ``group_b/cgroup.procs``. In cgroup v2 memory charges are never
> + *   transferred on task migration; they remain pinned to the cgroup
> + *   that allocated them. ``group_b/memory.current`` must not increase
> + *   beyond its baseline after the migration.
> + *
> + * Test 2 - New allocations charged to destination cgroup:
> + *   After migration the worker allocates an additional chunk of memory.
> + *   This new allocation must be charged to ``group_b``, so
> + *   ``group_b/memory.current`` must increase from the post-migration
> + *   baseline.
> + */
> +
> +#define _GNU_SOURCE
> +
> +#include <stdlib.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include "tst_test.h"
> +#include "memcontrol_common.h"
> +
> +#define ALLOC_SIZE	MB(60)
> +#define ALLOC_SIZE2	MB(20)
> +#define MIN_MEM_AVAIL	128
> +
> +static struct tst_cg_group *group_a;
> +static struct tst_cg_group *group_b;
> +static pid_t worker_pid;
> +
> +static void touch_pages(char *buf, size_t size)
> +{
> +	size_t i;
> +
> +	for (i = 0; i < size; i += getpagesize())
> +		buf[i] = 1;
> +}
> +
> +static void worker(void)
> +{
> +	char *buf1, *buf2;
> +
> +	SAFE_CG_PRINTF(group_a, "cgroup.procs", "%d", getpid());
> +
> +	buf1 = SAFE_MMAP(NULL, ALLOC_SIZE, PROT_READ | PROT_WRITE,
> +			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +	touch_pages(buf1, ALLOC_SIZE);
> +
> +	TST_CHECKPOINT_WAKE_AND_WAIT(0);
> +
> +	buf2 = SAFE_MMAP(NULL, ALLOC_SIZE2, PROT_READ | PROT_WRITE,
> +			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +	touch_pages(buf2, ALLOC_SIZE2);
> +
> +	TST_CHECKPOINT_WAKE(0);
> +
> +	pause();
> +}
> +
> +static void test_memcg_task_migration(void)
> +{
> +	long baseline_b, after_migrate, after_migrate_a, after_alloc2, current_a;
> +
> +	worker_pid = 0;
> +
> +	group_a = tst_cg_group_mk(tst_cg, "group_a");
> +	group_b = tst_cg_group_mk(tst_cg, "group_b");
> +
> +	if (SAFE_CG_HAS(tst_cg, "memory.swap.max")) {
> +		SAFE_CG_PRINT(group_a, "memory.swap.max", "0");
> +		SAFE_CG_PRINT(group_b, "memory.swap.max", "0");
> +	}
> +
> +	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &baseline_b);
> +	tst_res(TINFO, "group_b baseline memory.current=%ld", baseline_b);
> +
> +	worker_pid = SAFE_FORK();
> +	if (!worker_pid) {
> +		worker();
> +		exit(0);
> +	}
> +
> +	TST_CHECKPOINT_WAIT(0);
> +
> +	SAFE_CG_SCANF(group_a, "memory.current", "%ld", &current_a);
> +	TST_EXP_LE_LU(ALLOC_SIZE, current_a);
> +
> +	SAFE_CG_PRINTF(group_b, "cgroup.procs", "%d", worker_pid);
> +	tst_res(TINFO, "Migrated worker PID %d to group_b", worker_pid);
> +
> +	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &after_migrate);
> +	tst_res(TINFO,
> +		"group_b memory.current=%ld after migration (baseline=%ld)",
> +		after_migrate, baseline_b);
> +
> +	TST_EXP_LE_LU(after_migrate, baseline_b);

I do not think that it's actually guaranteed that nothing is charged in
the cgroup_b after the migration. I guess that we can use values_close()
function here.

> +	SAFE_CG_SCANF(group_a, "memory.current", "%ld", &after_migrate_a);
> +	tst_res(TINFO, "group_a memory.current=%ld after migration", after_migrate_a);
> +	TST_EXP_EXPR(after_migrate_a >= (long)ALLOC_SIZE,
> +		     "group_a memory.current (%ld) still holds pre-migration charges (>= ALLOC_SIZE %ld)",
> +		     after_migrate_a, (long)ALLOC_SIZE);
> +
> +	TST_CHECKPOINT_WAKE_AND_WAIT(0);
> +
> +	SAFE_CG_SCANF(group_b, "memory.current", "%ld", &after_alloc2);
> +	tst_res(TINFO, "group_b memory.current=%ld after second alloc (baseline=%ld)",
> +		after_alloc2, after_migrate);
> +
> +	TST_EXP_EXPR(after_alloc2 >= after_migrate + (long)ALLOC_SIZE2,
> +		     "group_b memory.current (%ld) increased by >= ALLOC_SIZE2 (%ld)",
> +		     after_alloc2, (long)ALLOC_SIZE2);

And here as well, I suppose that we can only assert that the
after_alloc2 >= ALLOC_SIZE2.

Also CCing Michal Koutny, our cgroup expert.

-- 
Cyril Hrubis
chrubis@suse.cz

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp