On 8/7/22 12:08 PM, Kanchan Joshi wrote: > On Sat, Aug 06, 2022 at 09:20:03AM -0600, Jens Axboe wrote: >> bdev based polled O_DIRECT is currently quite a bit faster than >> passthru on the same device, and one of the reaons is that we're not >> able to use the bio caching for passthru IO. >> >> If REQ_POLLED is set on the request, use the fs bio set for grabbing a >> bio from the caches, if available. This saves 5-6% of CPU over head >> for polled passthru IO. > > For passthru path, bio is always freed in the task-context (and not in > irq) so must this be tied to polled-io only? Right, that's why it's tied to polled. If polling gets cleared, then it will be freed normally on completion rather than inserted into the cache. I do have patches for irq bio caching too, that'll work fine with io_uring: https://git.kernel.dk/cgit/linux-block/commit/?h=perf-wip&id=ab3d4371227a34a5561e4d594a17baaad03bf1b7 I'll post that too, would be nice if we can figure out a clean way to do this. I have posted it before, iirc. -- Jens Axboe
