Re: Purpose of the mm/slab.c changes

[Ralf Baechle <ralf@conectiva.com.br>]

On Sun, Sep 09, 2001 at 01:58:44PM -0700, Davide Libenzi wrote:

> >> Do You see it as a plus ?
> >> The new allocated slab will be very likely written ( w/o regard
> >> about the old content ) and an L2 mapping will generate
> >> invalidate traffic.
> > 
> > If your invalidates are slower than your RAM, you should
> > consider getting another computer.
> 
> You mean a Sun, that uses a separate bus for snooping ? :)
> Besides to not under estimate the cache coherency traffic ( that on many CPUs
> uses the main memory bus ) there's the fact that the old data eventually
> present in L2 won't be used by the new slab user.

That's actually what having a slab cache of pre-initialized elements tries
to achieve.

On anything that uses a MESI-like cache coherence protocol a cached dirty
cache line that is written to will not cause any coherency traffic and
thus be faster.

  Ralf

--
"Embrace, Enhance, Eliminate" - it worked for the pope, it'll work for Bill.