On 10/12/2021 11:13 AM, Jens Axboe wrote: > External email: Use caution opening links or attachments > > > This memset in the fast path costs a lot of cycles on my setup. Here's a > top-of-profile of doing ~6.7M IOPS: > > + 5.90% io_uring [nvme] [k] nvme_queue_rq > + 5.32% io_uring [nvme_core] [k] nvme_setup_cmd > + 5.17% io_uring [kernel.vmlinux] [k] io_submit_sqes > + 4.97% io_uring [kernel.vmlinux] [k] blkdev_direct_IO > > and a perf diff with this patch: > > 0.92% +4.40% [nvme_core] [k] nvme_setup_cmd > > reducing it from 5.3% to only 0.9%. This takes it from the 2nd most > cycle consumer to something that's mostly irrelevant. > > Retain the full clear for the other commands to avoid doing any audits > there, and just clear the fields in the rw command manually that we > don't already fill. > > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> > > --- > Looks good to me. Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
