On 9/8/21 11:25 AM, Greg Kroah-Hartman wrote: > On Wed, Sep 08, 2021 at 11:06:51AM +0100, Pavel Begunkov wrote: >> Make read_iter_zero() to honor IOCB_NOWAIT, so /dev/zero can be >> advertised as FMODE_NOWAIT. This helps subsystems like io_uring to use >> it more effectively. Set FMODE_NOWAIT for /dev/null as well, it never >> waits and therefore trivially meets the criteria. > > I do not understand, why would io_uring need to use /dev/zero Not directly, users can issue I/O against it via io_uring. > and how is this going to help anything? For files not supporting nowait io_uring goes through a quite slow path. > What workload does this help with? Personally for me it's dumping output and benchmarking (not benchmarking /dev/zero, of course). But I'd also expect any tool that may be using it but rewritten with io_uring being able to normally use it without a performance hit. -- Pavel Begunkov
