Re: large page patch (fwd) (fwd)

Daniel Phillips
2002-08-10T18:58:06Z

On Saturday 10 August 2002 20:20, Eric W. Biederman wrote:
> Andrew Morton <akpm@zip.com.au> writes:
> > The other worry is the ZONE_NORMAL space consumption of pte_chains.
> > We've halved that, but it will still make high sharing levels
> > unfeasible on the big ia32 machines. We are dependant upon large
> > pages to solve that problem. (Resurrection of pte_highmem is in
> > progress, but it doesn't work yet).
>
> There is a second method to address this. Pages can be swapped out
> of the page tables and still remain in the page cache, the virtual
> scan does this all of the time. This should allow for arbitrary
> amounts of sharing. There is some overhead, in faulting the pages
> back in but it is much better than cases that do not work. A simple
> implementation would have a maximum pte_chain length.

Oh gosh, nice point. We could put together a lovely cooked benchmark where
copy_page_range just fails to copy all the mmap pages, which are most of them
in the bash test.

--
Daniel