[LTP] [PATCH v1] swapon01.c: Apply a margin to avoid oom

[Li Wang]

Hi Wei,

On Thu, Mar 14, 2024 at 9:33 AM Wei Gao via ltp <ltp@lists.linux.it> wrote:

> During our test i find a oom error during test which triggered by
> tst_pollute_memory.
>
> kernel:
> oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0-1,oom_memcg=/ltp/test-9552,task_memcg=/ltp/test-95520
> kernel: Memory cgroup out of memory: Killed process 9575 (swapon01)
> total-vm:1051484kB, anon-rss:1046572kB, file-rss:1280kB, shmem-rss:0k0
>
> Signed-off-by: Wei Gao <wegao@suse.com>
> ---
>  testcases/kernel/syscalls/swapon/swapon01.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/testcases/kernel/syscalls/swapon/swapon01.c
> b/testcases/kernel/syscalls/swapon/swapon01.c
> index d406e4bd9..357992525 100644
> --- a/testcases/kernel/syscalls/swapon/swapon01.c
> +++ b/testcases/kernel/syscalls/swapon/swapon01.c
> @@ -41,7 +41,9 @@ static void setup(void)
>         make_swapfile(SWAP_FILE, 10, 0);
>
>         SAFE_CG_PRINTF(tst_cg, "cgroup.procs", "%d", getpid());
> -       SAFE_CG_PRINTF(tst_cg, "memory.max", "%lu", TESTMEM);
> +
> +       /* Apply a margin to avoid oom during tst_pollute_memory */
> +       SAFE_CG_PRINTF(tst_cg, "memory.max", "%lu", TESTMEM + TESTMEM/100);
>

Even with a bit of margin added there is still not guarantee to avoid OOM
completely.

As the Cgroup V1 and V2 track memory and swap in two ways, if the margin is
too large that might not make the swap happen which is not our expectation.

So other method I can think of is to disable the OOM in Cgoup,
    echo 1 > memory.oom_control
or, set `overcommit_memory` to 2 to prevent the OOM from occurring.
    echo 2 > /proc/sys/vm/overcommit_memory




>  }
>
>  static struct tst_test test = {
> --
> 2.35.3
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>
>

-- 
Regards,
Li Wang