Re: [PATCH 2/4] slqb: Record what node is local to a kmem_cache_cpu

Mel Gorman
2009-10-01T15:16:51Z

On Thu, Oct 01, 2009 at 11:03:16AM -0400, Christoph Lameter wrote:
> On Thu, 1 Oct 2009, Mel Gorman wrote:
>
> > True, it might have been improved more if SLUB knew what local hugepage it
> > resided within as the kernel portion of the address space is backed by huge
> > TLB entries. Note that SLQB could have an advantage here early in boot as
> > the page allocator will tend to give it back pages within a single huge TLB
> > entry. It loses the advantage when the system has been running for a very long
> > time but it might be enough to skew benchmark results on cold-booted systems.
>
> The page allocator serves pages aligned to huge page boundaries as far as
> I can remember.

You're right, it does, particularly early in boot. It loses the advantage
when the system has been running a long time and memory is mostly full but
the same will apply to SLQB.

> You can actually use huge pages in slub if you set the max
> order to 9. So a page obtained from the page allocator is always aligned
> properly.
>

Fair point.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab