RE: [PATCH 0/7] Sparsemem Virtual Memmap V5

Christoph Lameter
2007-07-13T22:21:43Z

On Fri, 13 Jul 2007, Luck, Tony wrote:

> 1) There is a small performance regression for ia64 (which is promised
> to go away when bigger pages are used for the mem_map, but I'd like to
> see that this really does fix the issue).

The performance should be better than the existing one since we have even
less code here than discontig. We do no have to fetch the base anymore or
check boundaries (discontig was the baseline right?) but we have exactly
the same method of pfn_to_page and page_to_pfn as discontig/vmemmap.

These types of variation may come about due to the concurrency in memory
detection / reservations in the PROM on Altix systems which results in
variances in the placement of key memory areas. Performance often varies
slightly because of these issues.

If performance testing done on an Altix then the solution is to redo
the tests a couple of time, each time rebooting the box. Or redo it again
on a SMP box that does not have these variations.

How many tests were done and on what platform?