On Mon, 14 Oct 2024 at 23:27, Bernd Schubert <bernd.schubert@xxxxxxxxxxx> wrote:
> With only libfuse as ring user it is more like
>
> prep_requests(nr=N);
> wait_cq(1); ==> we must not wait for more than 1 as more might never arrive
> io_uring_for_each_cqe {
> }
Right.
I think the point Pavel is trying to make is that io_uring queue
sizes don't have to match fuse queue size. So we could have
sq_entries=4, cq_entries=4 and have the server queue 64
FUSE_URING_REQ_FETCH commands, it just has to do that in batches of 4
max.
> @Miklos maybe we avoid using large CQEs/SQEs and instead set up our own
> separate buffer for FUSE headers?
The only gain from this would be in the case where the uring is used
for non-fuse requests as well, in which case the extra space in the
queue entries would be unused (i.e. 48 unused bytes in the cacheline).
I don't know if this is a realistic use case or not. It's definitely
a challenge to create a library API that allows this.
The disadvantage would be a more complex interface.
Thanks,
Miklos
