Re: [PATCH] [2.6] [2/2] hlist: remove IFs from hlist functions

[Alex Pankratov]

Andi Kleen wrote:

> Alex Pankratov <ap@xxxxxxxxxx> writes:
>
> > No, because its 'pprev' field *is* getting modified.
>
> I didn't notice this before, sorry. But this could end up 
> being a scalability problem on big SMP systems. Even though
> the cache line of this is never read it will bounce all the
> time between all CPUs using hlists and add considerably 
> latency and cross node traffic. Remember Linux is supposed
> to run well on 128 CPU machines now.

That's a bit above my head. How does this potential latency
compare to the speed up due to not having CMPs ? My cycle
counting skills are a bit dusty :)

> Maybe you can make it UP only, but I'm still not sure it's 
> worth it.

Sorry, I didn't the 'UP' part.
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