On Tue, Mar 13, 2018 at 07:40:51PM +0200, Michael S. Tsirkin wrote: > I think it's a good idea to use sysfs for this. However, > there are a couple of missing interfaces here: > > 1. Userspace needs a way to know when this value changes. > I see no change notifications here and that does not seem right.
How can these change? > 2. Userspace needs to be able to read these without > system calls. Ick, what? Why not? > Pls add mmap support to the raw format. For a single integer? Why do you need mmap for this? What is so "performant" that needs to touch a sysfs file? > (Phys address is not guaranteed to be page-aligned so you will > probably want an offset attribute for that as well). Ick ick ick, that's why it's good to just stick with a sysfs file. Have you tested just how long this takes to see if the open/read/close is really the bottleneck, or if the io on reading the value is the bottleneck? thanks, greg k-h
