On Sat, 2 Apr 2022 at 03:17, Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 4/1/22 10:21 AM, Jens Axboe wrote: > > On 4/1/22 10:02 AM, Miklos Szeredi wrote: > >> On Fri, 1 Apr 2022 at 17:36, Jens Axboe <axboe@xxxxxxxxx> 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. > > > > fput() isn't sync, it'll just offload to task_work. There are some > > dependencies there that would need to be checked. But we'll find a way > > to deal with it. > > > >> 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. > > > > OK, I'll check up on this, but probably won't have time to do so before > > early next week. > > Can you try with this patch? It's not complete yet, there's actually a > bunch of things we can do to improve the direct descriptor case. But > this one is easy enough to pull off, and I think it'll fix your OOM > case. Not a proposed patch, but it'll prove the theory. Sorry for the delay.. Patch works like charm. Thanks, Miklos
