[lkml]   [2005]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC 1/3] Framework for accurate node based statistics
On Tue, Dec 06, 2005 at 11:36:43AM -0800, Christoph Lameter wrote:
> On Tue, 6 Dec 2005, Andi Kleen wrote:
> > > Yuck. That code uses atomic operations and is not aware of atomic64_t.
> > Hmm? What code are you looking at?
> include/asm-generic/local.h. this is the default right? And
> include/asm-ia64/local.h.
> > At least i386/x86-64/generic don't use any atomic operations, just
> > normal non atomic on bus but atomic for interrupts local rmw.
> inc/dec are atomic by default on x86_64?

They are atomic against interrupts on the same CPU. And on Linux
also atomic against preempt moving you to another CPU. And all that
without the cost of a bus lock. And that is what local_t is about.

> > Do you actually need 64bit?
> 32 bit limits us in the worst case to 8 Terabytes of RAM (assuming a very
> small page size of 4k and 31 bit available for an atomic variable
> [sparc]). SGI already has installations with 15 Terabytes of RAM.

Ok we'll need a local64_t then. No big deal - can be easily added.
Or perhaps better a long_local_t so that 32bit doesn't need to
pay the cost.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-12-06 21:08    [from the cache]
©2003-2014 Jasper Spaans. hosted at Digital Ocean