Re: larger default page sizes...

Christoph Lameter
2008-03-25T17:48:19Z

On Mon, 24 Mar 2008, David Miller wrote:

> We should fix the underlying problems.
>
> I'm hitting issues on 128 cpu Niagara2 boxes, and it's all fundamental
> stuff like contention on the per-zone page allocator locks.
>
> Which is very fixable, without going to larger pages.

No its not fixable. You are doing linear optimizations to a slowdown that
grows exponentially. Going just one order up for page size reduces the
necessary locks and handling of the kernel by 50%.

> > powerpc also runs HPC codes. They certainly see the same results
> > that we see.
>
> There are ways to get large pages into the process address space for
> compute bound tasks, without suffering the well known negative side
> effects of using larger pages for everything.

These hacks have limitations. F.e. they do not deal with I/O and
require application changes.