Messages in this thread | | | Date | Wed, 14 Mar 2018 19:25:36 +0100 | From | Greg KH <> | Subject | Re: [PATCH v5] drivers/misc: vm_gen_counter: initial driver implementation |
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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
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