Re: [PATCH] Rmap speedup

Andrew Morton
2002-08-03T21:30:21Z

Rik van Riel wrote:
>
> On Fri, 2 Aug 2002, Andrew Morton wrote:
>
> > No joy, I'm afraid.
>
> > Guess we should instrument it up and make sure that the hashing
> > and index thing is getting the right locality.
>
> Could it be that your quad needs to go to RAM to grab a cacheline
> that's exclusive on the other CPU while Daniel's machine can just
> shove cachelines from CPU to CPU ?

Could be, Rik. I don't know. It's a bit worrisome that we might
be dependent on subtleties like that.

> What I'm referring to is the fact that the pte_chain_locks in
> Daniel's patch are all packed into a few cachelines, instead of
> having each lock on its own cache line...
>
> This could explain the fact that the locking overhead plummeted
> on Daniel's box while it didn't change at all on your machine.

Oh it helped a bit. More in 2.4 than 2.5. Possibly I broke
Daniel's patch somehow. But even the improvement in 2.4
from Daniel's patch is disappointing.