Re: [LTP] [PATCH] memcg_control_test: Disable swapping in test cgroup

[Petr Vorel <pvorel@suse.cz>]

Hi,

> 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, and no OOM kill to occur which results in a test
> failure. Fix this by disabling swap in the test cgroup if it is enabled,
> causing both pages to always be accounted under the same counter such
> that memory.max (v2) / memory.limit_in_bytes (v1) causes an OOM kill.

LGTM.
Reviewed-by: Petr Vorel <pvorel@suse.cz>

I suppose the old shell tests which cgroupv1 memory.memsw.limit_in_bytes are
written to test memory limits, thus only this one is suitable to modify.

The new C based tests (cgroupv2) should not be affected either.

Kind regards,
Petr

> Fixes: c0b815736 ("New testcase added by Naufal.")
> Signed-off-by: T.J. Mercier <tjmercier@google.com>
> ---
>  .../kernel/controllers/memcg/control/memcg_control_test.sh   | 5 ++---
>  1 file changed, 2 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..eb8db3e30 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 +49,13 @@ 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"
> +		ROD echo 0 \> "$test_dir/$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"

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