On Fri, 1 Apr 2022 at 17:36, Jens Axboe <axboe@kernel.dk> wrote:

> I take it you're continually reusing those slots?

Yes.

>  If you have a test
> case that'd be ideal. Agree that it sounds like we just need an
> appropriate breather to allow fput/task_work to run. Or it could be the
> deferral free of the fixed slot.

Adding a breather could make the worst case latency be large.  I think
doing the fput synchronously would be better in general.

I test this on an VM with 8G of memory and run the following:

./forkbomb 14 &
# wait till 16k processes are forked
for i in `seq 1 100`; do ./procreads u; done

You can compare performance with plain reads (./procreads p), the
other tests don't work on public kernels.

Thanks,
Miklos