Re: large page patch (fwd) (fwd)

David Mosberger
2002-08-03T21:22:59Z

>>>>> On Sat, 3 Aug 2002 16:53:39 -0400, Hubertus Franke <frankeh@watson.ibm.com> said:

Hubertus> Cool. Does that mean that BSD already has page coloring
Hubertus> implemented ?

FreeBSD (at least on Alpha) makes some attempts at page-coloring, but
it's said to be far from perfect.

Hubertus> The agony is: Page Coloring helps to reduce cache
Hubertus> conflicts in low associative caches while large pages may
Hubertus> reduce TLB overhead.

Why agony? The latter helps the TLB _and_ solves the page coloring
problem (assuming the largest page size is bigger than the largest
cache; yeah, I see that could be a problem on some Power 4
machines... ;-)

Hubertus> One shouldn't rule out one for the other, there is a place
Hubertus> for both.

Hubertus> How did you arrive to the (weak) empirical evidence? You
Hubertus> checked TLB misses and cache misses and turned page
Hubertus> coloring on and off and large pages on and off?

Yes, that's basically what we did (there is a patch implementing a
page coloring kernel module floating around).

--david