Re: RFC: CONFIG_PAGE_SHIFT (aka software PAGE_SIZE)

Dave Hansen
2007-07-12T16:36:00Z

On Thu, 2007-07-12 at 18:31 +0200, Andrea Arcangeli wrote:
> On Fri, Jul 13, 2007 at 12:44:49AM +1000, David Chinner wrote:
> > That's crap. Just because a machine has lots of memory does not
> > make it OK to waste lots of memory.
>
> It's not just wasted, it lowers overhead all over the place. Yes, the
> benefit of wasting less pagecache may largely outweight the benefit of
> having a larger page size, but if you've a lot of memory perhaps your
> working set already fits in the cache, or perhaps you don't fit in the
> cache regardless of the page size.

Have you guys seen Shaggy's page cache tails?

http://kernel.org/pub/linux/kernel/people/shaggy/OLS-2006/kleikamp.pdf

We've had the same memory waste issue on ppc64 with 64k hardware
pages.

-- Dave