On 10/11/24 19:57, Jens Axboe wrote: > On 10/10/24 2:56 PM, Bernd Schubert wrote: >> Hello, >> >> as discussed during LPC, we would like to have large CQE sizes, at least >> 256B. Ideally 256B for fuse, but CQE512 might be a bit too much... >> >> Pavel said that this should be ok, but it would be better to have the CQE >> size as function argument. >> Could you give me some hints how this should look like and especially how >> we are going to communicate the CQE size to the kernel? I guess just adding >> IORING_SETUP_CQE256 / IORING_SETUP_CQE512 would be much easier. > > Not Pavel and unfortunately I could not be at that LPC discussion, but > yeah I don't see why not just adding the necessary SETUP arg for this > would not be the way to go. As long as they are power-of-2, then all > it'll impact on both the kernel and liburing side is what size shift to > use when iterating CQEs. Thanks, Pavel also wanted power-of-2, although 512 is a bit much for fuse. Well, maybe 256 will be sufficient. Going to look into adding that parameter during the next days. > > Since this obviously means larger CQ rings, one nice side effect is that > since 6.10 we don't need contig pages to map any of the rings. So should > work just fine regardless of memory fragmentation, where previously that > would've been a concern. > Out of interest, what is the change? Up to fuse-io-uring rfc2 I was vmalloced buffers for fuse that got mmaped - was working fine. Miklos just wants to avoid that kernel allocates large chunks of memory on behalf of users. Thanks, Bernd
