On 5/3/21 10:12 AM, David Laight wrote: > From: Jens Axboe >> Sent: 03 May 2021 15:58 >> >> Had a report on writing to eventfd with io_uring is slower than it >> should be, and it's the usual case of if a file type doesn't support >> ->write_iter(), then io_uring cannot rely on IOCB_NOWAIT being honored >> alongside O_NONBLOCK for whether or not this is a non-blocking write >> attempt. That means io_uring will punt the operation to an io thread, >> which will slow us down unnecessarily. >> >> Convert eventfd to using fops->write_iter() instead of fops->write(). > > Won't this have a measurable performance degradation on normal > code that does write(event_fd, &one, 4); If ->write_iter() or ->read_iter() is much slower than the non-iov versions, then I think we have generic issues that should be solved. That should not be a consideration, since the non-iov ones are legacy and should not be adopted in new code. -- Jens Axboe
