On 3/10/23 12:04?PM, Pavel Begunkov wrote: > io_uring extensively uses task_work, but when a task is waiting > for multiple CQEs it causes lots of rescheduling. This series > is an attempt to optimise it and be a base for future improvements. > > For some zc network tests eventually waiting for a portion of > buffers I've got 10x descrease in the number of context switches, > which reduced the CPU consumption more than twice (17% -> 8%). > It also helps storage cases, while running fio/t/io_uring against > a low performant drive it got 2x descrease of the number of context > switches for QD8 and ~4 times for QD32. > > Not for inclusion yet, I want to add an optimisation for when > waiting for 1 CQE. Ran this on the usual peak benchmark, using IRQ. IOPS is around ~70M for that, and I see context rates of around 8.1-8.3M/sec with the current kernel. Applied the two patches, but didn't see much of a change? Performance is about the same, and cx rate ditto. Confused... As you probably know, this test waits for 32 ios at the time. Didn't take a closer look just yet, but I grok the concept. One immediate thing I'd want to change is the FACILE part of it. Let's call it something a bit more straightforward, perhaps LIGHT? Or LIGHTWEIGHT? I can see this mostly being used for filling a CQE, so it could also be named something like that. But could also be used for light work in the same vein, so might not be a good idea to base the naming on that. -- Jens Axboe
