Re: Maybe a VM bug in 2.4.18-18 from RH 8.0?

William Lee Irwin III
2002-12-07T00:14:11Z

> William Lee Irwin III wrote:
> >
> > ...
> > A 16KB or 64KB kernel allocation unit would then annihilate
>
On Fri, Dec 06, 2002 at 04:01:24PM -0800, Andrew Morton wrote:
> You want to be careful about this:
> CPU: L1 I cache: 16K, L1 D cache: 16K
> Because instantiating a 16k page into user pagetables in
> one hit means that it must all be zeroed. With these large
> pagesizes that means that the application is likely to get
> 100% L1 misses against the new page, whereas it currently
> gets 100% hits.

16K is reasonable; after that one might as well go all the way.
About the only way to cope is amortizing it by cacheing zeroed pages,
and that has other downsides.

Bill