[LTP] mmapstress06: Rate limit page-dirtying loop to prevent MemCG OOM-kills

[linuxtestproject.agent@gmail.com]

Hi Wei,

On Tue, Aug 25, 2026, Wei Gao wrote:
> mmapstress06: Rate limit page-dirtying loop to prevent MemCG OOM-kills

> +		/*
> +		 * Yield periodically to space out allocation spikes and allow
> +		 * asynchronous swap writeback to catch up on slower VM disks.
> +		 */
>  		for (size_t i = 0; i < map_size; i += page_size) {
>  			mmapaddr[i] = 'a';
> -			if ((i % (2 * 1024 * 1024)) == 0)
> -				usleep(1000);
> +			if ((i % (64 * 1024)) == 0)
> +				usleep(200);

Could this avoid using a fixed sleep to synchronize with asynchronous swap
writeback? The 7.2 cgroup documentation says memory.max invokes the cgroup OOM
killer when reclaim cannot reduce usage, while the delay here is unrelated to
actual reclaim progress. A swap device slower than the chosen dirtying rate
can therefore still OOM-kill the child and make the test fail for
environmental timing reasons. Please use reclaim throttling or poll observable
progress with backoff instead of tuning a fixed delay.

Verdict - Needs revision

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