Re: [patch][rfc] remove ZERO_PAGE?

Nick Piggin
2007-07-27T05:54:07Z

On Thu, Jul 26, 2007 at 10:29:01PM -0700, Linus Torvalds wrote:
>
>
> On Fri, 27 Jul 2007, Nick Piggin wrote:
> >
> > I'd like to see if we can get the ball rolling on this again, and try to
> > get it in 2.6.24 maybe. Any comments?
>
> I'd really want real performance numbers. I don't like the "remove it
> because I don't like it". I want real numbers for real loads before I'm
> really interested.

What numbers, though? I can make up benchmarks to show that ZERO_PAGE
sucks just as much. The problem I don't think is finding a situatoin that
improves without it (we have an extreme case where the Altix livelocked)
but to get confidence that nothing is going to blow up.

> Last time this came up, the logic behind wanting to remove the zero page
> was all screwed up, and it was all based on totally broken premises. So I
> really want somethign else than just "I don't like it".

I thought that last time this came up you thought it might be good to
try out in -mm initially.

> Sorry. In the absense of numbers (and not just some made-up branchmark:
> something real - I can _easily_ make benchmarks that show that ZERO_PAGE
> is wonderful), I'm not at all interested.

OK, well what numbers would you like to see? I can always try a few
things.