Re: RFC: NAPI packet weighting patch

[Andi Kleen <ak@xxxxxxx>]

On Wed, Jun 22, 2005 at 03:53:30PM -0600, Chris Friesen wrote:
> Andi Kleen wrote:
> 
> >8 entries? That sounds very small. Is that an old Sparc or something? :)
> 
> The G5 has 8 prefetch streams.  Not an ancient cpu.

prefetch stream means a context of the auto prefetcher. 

It different from a load queue entry which is just a load of a cache line
which can be triggered by user instructions or the auto prefetcher. 
Each prefetch stream would consume a lot of them, so just for your 8 streams 
above you probably need a large two digit number or more.

I don't have exact numbers for the PPC970, but afaik its LS unit
has a very long queue. On POWER4 (which is a very similar CPU) we see 
a lot of races that don't happen on other platforms. That seems to be 
because it reorders writes every aggressively. I suppose this is true for
reads as well.

-Andi