Re: [rfc] no ZERO_PAGE?

Dan Aloni
2007-04-04T13:55:32Z

On Wed, Apr 04, 2007 at 02:27:01PM +0200, Andrea Arcangeli wrote:
> On Wed, Apr 04, 2007 at 12:24:07PM +0200, Nick Piggin wrote:
> > But for a potential mainline merge, maybe starting with a CONFIG
> > option is a good idea -- defaulting to off, and we could start by
> > turning it on just in -rc kernels for a few releases, to get a bit
> > more confidence?
>
> The only reason to do that is if there are many stupid apps pretending
> to get meaningful information from pages that cannot contain any
> information. The zero page in the anon page fault has been there
> forever so...

There might be a lot of applications like that, and I'm not sure that
_all_ of them can be considered 'stupid' as you say.

How about applications that perform mmap() and R/W random-access on
large *sparse* files? (e.g. a scientific app that uses a large sparse
file as a big database look-up table). As I see it, these apps would
need to keep track of what's sparse and what's not...

--
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il