[LTP] [PATCH] memcg_control_test: Disable swapping in test cgroup for v2

[Li Wang]

On Fri, Mar 28, 2025 at 4:01 AM T.J. Mercier via ltp <ltp@lists.linux.it>
wrote:

> memcg_control_test_1 sets both a memory limit and a memsw/swap limit to
> a single page, and then asks mem_process to allocate 2 pages in an
> attempt to cause a memcg OOM kill. However, if swapping is enabled the
> first page can be swapped before the second is allocated causing neither
> limit to be exceeded in v2 since there is no combined memsw counter in
> v2. In this case no OOM kill will occur which results in a test failure.
> Fix this by disabling swap in the test cgroup for v2 if swap is enabled,
> causing both pages to always be accounted under the same counter such
> that memory.max causes an OOM kill.
>
> Fixes: c0b815736 ("New testcase added by Naufal.")
> Signed-off-by: T.J. Mercier <tjmercier@google.com>
>

Reviewed-by: Li Wang <liwang@redhat.com>

---
>  .../memcg/control/memcg_control_test.sh            | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git
> a/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
> b/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
> index 68287a70c..79b3a02a9 100644
> --- a/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
> +++ b/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
> @@ -12,7 +12,6 @@ TST_NEEDS_TMPDIR=1
>
>  PAGE_SIZE=$(tst_getconf PAGESIZE)
>
> -TOT_MEM_LIMIT=$PAGE_SIZE
>  ACTIVE_MEM_LIMIT=$PAGE_SIZE
>  PROC_MEM=$((PAGE_SIZE * 2))
>
> @@ -50,13 +49,22 @@ test1()
>
>         # If the kernel is built without swap, the $memsw_memory_limit
> file is missing
>         if [ -e "$test_dir/$memsw_memory_limit" ]; then
> -               ROD echo "$TOT_MEM_LIMIT" \>
> "$test_dir/$memsw_memory_limit"
> +               if [ "$cgroup_version" = "2" ]; then
> +                       # v2 does not have a combined memsw limit like v1.
> +                       # Disable swapping in v2 so all pages get
> acccounted to the non-swap counter.
> +                       SWAP_LIMIT=0
> +               else
> +                       # Swapping cannot be disabled via
> memsw.limit_in_bytes in v1.
> +                       # Apply a memsw limit in v1 to capture any swapped
> pages
> +                       SWAP_LIMIT=$ACTIVE_MEM_LIMIT
> +               fi
> +               ROD echo "$SWAP_LIMIT" \> "$test_dir/$memsw_memory_limit"
>         fi
>
>         KILLED_CNT=0
>         test_proc_kill
>
> -       if [ $PROC_MEM -gt $TOT_MEM_LIMIT ] && [ $KILLED_CNT -eq 0 ]; then
> +       if [ $KILLED_CNT -eq 0 ]; then
>                 tst_res TFAIL "Test #1: failed"
>         else
>                 tst_res TPASS "Test #1: passed"
> --
> 2.49.0.472.ge94155a9ec-goog
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>
>

-- 
Regards,
Li Wang