[LTP] [PATCH v2] memcg/functional: fix memcg_failcnt intermittent timeout by disabling swap

[Xuewen Wang]

Hi Li Wang,
Thank you for the review and the suggestions. I've sent v3 with the changes you proposed:

- Move swapoff to do_setup() and swapon to do_cleanup()
- Adjust the order in do_cleanup() to swapon first, then memcg_cleanup

Please take a look when you have time.
Best regards,
Xuewen Wang

在 2026/8/5 15:34, Li Wang 写道:
> Hi Xuewen,
> 
> Xuewen Wang wrote:
> 
>> memcg_failcnt.sh tests the memory.failcnt counter by allocating
>> reclaimable memory (mmap-anon/mmap-file/shm) beyond a tiny cgroup
>> limit (1 page). It relies on the process being OOM-killed so that
>> signal_memcg_process()'s wait loop exits.
>>
>> With swap enabled the kernel usually still OOM-kills the process,
>> but on arm64 reclaim (swap out) sometimes succeeds instead:
>> usage_in_bytes stays at the limit and the process keeps running,
>> so the wait loop times out (TBROK) intermittently.
>>
>> Example failure on arm64 (kernel 6.6):
>>   memcg_failcnt 2 TBROK: timed out on memory.usage_in_bytes 4096 0 8192
>>
>> Disable swap around the allocation and re-enable it afterwards,
>> mirroring what memcg_limit_in_bytes.sh already does for the same
>> reclaimable memory types.
> 
> This fix make sense, but I'd rather go with a tidy way:
> 
> ...
> TST_SETUP=do_setup
> TST_CLEANUP=do_cleanup
> 
> do_setup()
> {
>         memcg_setup
>         swapoff -a
> }
> 
> do_cleanup()
> {
>         swapon -a
>         memcg_cleanup
> }
> 
> ...
> 
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> address for future versions:
> 
>   li.wang@linux.dev
> or:
>   liwang@hygon.cn
>