Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()

[Paul Jackson <pj@sgi.com>]

Interesting - thanks Andi.

I had one of my colleagues at SGI lobby me hard for such a facility.
I'll see if I can get him on this thread to better explain what he
wanted it for.

Roughly, he was looking to support something resembling the kernel's
per-cpu data in userland library code for high performance scientific
number crunching, for things like statistics gathering and perhaps (not
sure of this) reduce locking costs.

I see "x86-64" in the Subject.  I don't see why this facility is
arch-specific.  Could it work on any arch, ia64 being the one of
interest to me?

I have some ignorance on your references to "CPUID(1)".  I don't recall
what it is.  The only command so named I find on my systems are a
Windows command from the year 1999.  I doubt that's it.  You wrote:

> As you can see CPUID(1) is always very slow

but but I don't see any stats above the comment mentioning CPUID(1),
so ... er eh ... no I don't see.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401