Re: 2.4.19/20, 2.5 missing P4 ifdef ?

["J.A. Magallon" <jamagallon@able.es>]

On 2002.11.28 Dave Jones wrote:
>On Thu, Nov 28, 2002 at 03:17:53PM +0100, Margit Schubert-While wrote:
> > Just noticed this in "include/asm-i386/processor.h" :
> > 
> > --- snip ---
> > /* Prefetch instructions for Pentium III and AMD Athlon */
> > #ifdef  CONFIG_MPENTIUMIII
> > #define ARCH_HAS_PREFETCH
> > extern inline void prefetch(const void *x)
> > {
> >         __asm__ __volatile__ ("prefetchnta (%0)" : : "r"(x));
> > }
> > #elif CONFIG_X86_USE_3DNOW
> > --- end snip ---
> > 
> > The P4 has SSE and prefetch or no ?
>
>It does. You seem to have found a bug.
>

Two questions:
- I am trying to use gcc's __builtin_prefetch, and it is able to
  spit different prefetch instructions depending on 'temporal
  locality' of the data:
	prefetchnta, prefetcht2, prefetcht1, prefetcht0
temp-loc:    0           1         2           3
  0 means you can just discard after r or w, and 3 means you
  are really interested in data lasting in cache.
  Do not know if the use of prefetch in kernel is extensive,
  but perhaps this is something to investigate...

- PII also supports the prefetches. Is it worth to add it ?

TIA

-- 
J.A. Magallon <jamagallon@able.es>      \                 Software is like sex:
werewolf.able.es                         \           It's better when it's free
Mandrake Linux release 9.1 (Cooker) for i586
Linux 2.4.20-rc4-jam0 (gcc 3.2 (Mandrake Linux 9.1 3.2-4mdk))