On 1/22/20 4:59 AM, Michal Hocko wrote: > On Tue 21-01-20 20:57:23, Jerome Glisse wrote: >> We can also discuss what kind of knobs we want to expose so that >> people can decide to choose the tradeof themself (ie from i want low >> latency io-uring and i don't care wether mm can not do its business; to >> i want mm to never be impeded in its business and i accept the extra >> latency burst i might face in io operations). > > I do not think it is a good idea to make this configurable. How can > people sensibly choose between the two without deep understanding of > internals? Fully agree, we can't just punt this to a knob and call it good, that's a typical fallacy of core changes. And there is only one mode for io_uring, and that's consistent low latency. If this change introduces weird reclaim, compaction or migration latencies, then that's a non-starter as far as I'm concerned. And what do those two settings even mean? I don't even know, and a user sure as hell doesn't either. io_uring pins two types of pages - registered buffers, these are used for actual IO, and the rings themselves. The rings are not used for IO, just used to communicate between the application and the kernel. -- Jens Axboe
