[LTP] [PATCH v2] controllers/memcg: Add testcase for kmem_limit_in_bytes of memory cgroup

[Richard Palethorpe]

Hello,

Zhao Gongyi <zhaogongyi@huawei.com> writes:

> Add memory cgroup testcase for checking that kmem overflow is controlled
> by kmem.limit_in_bytes.

I am currently working on a new LTP CGroups API, please see:
https://patchwork.ozlabs.org/project/ltp/list/?series=238773

If the new API is merged quickly, then this test will need to be
converted to it. Also please see comments below.

>
> Signed-off-by: Zhao Gongyi <zhaogongyi@huawei.com>
> ---
> v1->v2:
> 	1) add testcase to runtest/controllers
> 	2) add testcase to testcases/kernel/controllers/memcg/.gitignore
> ---
>  runtest/controllers                           |  1 +
>  testcases/kernel/controllers/memcg/.gitignore |  1 +
>  .../functional/memcg_kmem_limit_in_bytes.c    | 87 +++++++++++++++++++
>  3 files changed, 89 insertions(+)
>  create mode 100644 testcases/kernel/controllers/memcg/functional/memcg_kmem_limit_in_bytes.c
>
> diff --git a/runtest/controllers b/runtest/controllers
> index e3d0243f1..f13a112c7 100644
> --- a/runtest/controllers
> +++ b/runtest/controllers
> @@ -15,6 +15,7 @@ memcg_use_hierarchy	memcg_use_hierarchy_test.sh
>  memcg_usage_in_bytes	memcg_usage_in_bytes_test.sh
>  memcg_stress		memcg_stress_test.sh
>  memcg_control		memcg_control_test.sh
> +memcg_kmem_limit_in_bytes memcg_kmem_limit_in_bytes
>
>  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 c0b6d0714..dce8412de 100644
> --- a/testcases/kernel/controllers/memcg/.gitignore
> +++ b/testcases/kernel/controllers/memcg/.gitignore
> @@ -1,5 +1,6 @@
>  /control/mem_process
>  /functional/memcg_process
> +/functional/memcg_kmem_limit_in_bytes
>  /regression/memcg_test_1
>  /regression/memcg_test_2
>  /regression/memcg_test_3
> diff --git a/testcases/kernel/controllers/memcg/functional/memcg_kmem_limit_in_bytes.c b/testcases/kernel/controllers/memcg/functional/memcg_kmem_limit_in_bytes.c
> new file mode 100644
> index 000000000..61f3f6fd5
> --- /dev/null
> +++ b/testcases/kernel/controllers/memcg/functional/memcg_kmem_limit_in_bytes.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2021 HUAWEI LIMITED
> + * Author: Zhao Gongyi <zhaogongyi@huawei.com>
> + */
> +
> +/*\
> + * [Description]
> + * Check that kmem overflow is controlled by kmem.limit_in_bytes.
> + *
> + * [Algorithm]
> + * 1) mount memory cgroup
> + * 2) set 0 to memory.kmem.limit_in_bytes
> + * 3) set test process group to cgroup.procs
> + * 4) fork in test process group to trig kmem overflow
> + */
> +
> +#include <sys/wait.h>
> +#include "tst_test.h"
> +
> +#define MNT_POINT "memcg"
> +#define TESTDIR "memcg/ltpmemcg"
> +#define CGROUP_PROCS "memcg/ltpmemcg/cgroup.procs"
> +#define KMEM_LIMIT_IN_BYTES "memcg/ltpmemcg/memory.kmem.limit_in_bytes"
> +
> +static void cleanup(void)
> +{
> +	SAFE_RMDIR(TESTDIR);
> +	SAFE_UMOUNT(MNT_POINT);
> +	SAFE_RMDIR(MNT_POINT);
> +}
> +
> +static void setup(void)
> +{
> +	SAFE_MKDIR(MNT_POINT, 0755);
> +	SAFE_MOUNT("memcg", MNT_POINT, "cgroup", 0, "memory");
> +	SAFE_MKDIR(TESTDIR, 0755);
> +}
> +
> +static void run(void)
> +{
> +	pid_t pid;
> +	int st;
> +
> +	pid = SAFE_FORK();
> +	if (!pid) {
> +		SAFE_SETPGID(0, 0);
> +
> +		SAFE_FILE_PRINTF(KMEM_LIMIT_IN_BYTES, "%d", 0);
> +
> +		SAFE_FILE_PRINTF(CGROUP_PROCS, "%d", getpgid(getpid()));

After setting this we should avoid doing any work in this process except
calling fork. AFAIK there is no guarantee that some other syscall or
tasklet etc. Won't try to allocate memory and also fail.

> +
> +		TEST(fork());
> +		if (TST_RET == -1) {
> +			if (TST_ERR == ENOMEM)
> +				tst_res(TPASS, "fork fail as expected");
> +			else
> +				tst_brk(TFAIL | TTERRNO,
> +					"fork fail as unexpected");

This should be "fork failed with unexpected error".

> +		} else if (TST_RET == 0) {
> +			tst_brk(TFAIL, "fork success as unexpected");
> +		} else {
> +			SAFE_WAIT(NULL);
> +			tst_brk(TFAIL, "fork success as unexpected");
> +		}
> +	} else {
> +		SAFE_WAIT(&st);
> +		if (WIFEXITED(st))
> +			if (!WEXITSTATUS(st)) {
> +				tst_res(TPASS, "kmem alloc is controled "
> +					"by memory.kmem.limit_in_bytes");
> +				return;
> +			}
> +
> +		tst_res(TFAIL,"kmem alloc is not controled "
> +			"by memory.kmem.limit_in_bytes");
> +	}
> +}
> +
> +static struct tst_test test = {
> +	.needs_root = 1,
> +	.needs_tmpdir = 1,
> +	.forks_child = 1,
> +	.setup = setup,
> +	.test_all = run,
> +	.cleanup = cleanup,
> +};
> --
> 2.17.1


-- 
Thank you,
Richard.