Mailinglist Archive: opensuse-amd64 (203 mails)

["William A. Mahaffey III" <wam@xxxxxxxxxx>]

Andi Kleen wrote:

> On Thu, 30 Jun 2005 11:02:34 -0700
> Sheo Shanker Prasad <ssp@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>  
>
> > (5) My puzzle:
> >
> > While a computer is well known to be reproducible, the wild variation by a 
> > factor of almost 3 in the execution is very disturbing. 
> >    
>
> It could be cache effects. Linux does not do enforced L2 cache
> coloring while allocating user memory so in memory intensive programs
> some variation can happen depending on how well the cache is used.
> However an Opteron has a 16 way associative L2 cache so such
> things normally don't happen there.
>
> One difference between 9.1 and 9.3 is that 9.3 allocates the memory
> from the start to the end after boot up, while 9.1 tended to allocate
> it from up to down (highest memory first). It is possible that
> your BIOS has a broken MTRR or somesuch and that some low page
> is not cached properly and slowing things down. If it was a high
> page it could be avoided by booting with mem=...M with a number
> smaller than your memory. However for low pages that's difficult.
>
> -Andi
>
>
>  

Is that difference twixt allocation protocols a 2.4.x kernel vs. 2.6.n 
kerrnel difference (i.e. generic to ANY AMD64 linux) or something else ?

--
	William A. Mahaffey III
---------------------------------------------------------------------
	Remember, ignorance is bliss, but
	willful ignorance is LIBERALISM !!!!