Re: [PATCH] Rmap speedup

[Andrew Morton]

Daniel Phillips wrote:
> 
> This patch eliminates about 35% of the raw rmap setup/teardown overhead by
> adopting a new locking interface that allows the add_rmaps to be batched in
> copy_page_range.

Well that's fairly straightforward, thanks.  Butt-ugly though ;)

Don't bother doing teardown yet.  I have patches which batch
all the zap_page_range activity into 16-page chunks, so we
eventually end up in a single function with 16 virtually-contiguous
pages to release.  Adding the batched locking to that will
be simple.

Sigh.  I have a test which sends the 2.5.30 VM into a five-minute
coma and which immediately panics latest -ac with pte_chain oom.
Remind me again why all this is worth it?

I'll port your stuff to 2.5 over the weekend, let you know...