[PATCH 4/5] Add a sysconf syscall

[Andrew Lutomirski]

On Mon, May 16, 2011 at 12:08 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> You could also add a vsyscall function and have that function pull the
>> values from vvar data.  It would be very fast (i.e. almost as fast as
>> mmaping some data) and it would be more portable.
>
> vvar is a global. The variable data in sysconf is per thread
> (and not even per mm)
>
> Even if you ignore the semantic problem of thread versus mm, you would
> need a new writable page per process and update it any time
> the rlimits and other information is updated.
>
> On the other hand my solution is dead simple and already solves
> the problem.

True.  I should read the entire list of variables before making
suggestions that won't work.  :)

--Andy

>
> -Andi
>