lkml.org 
[lkml]   [2007]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: remove zero_page (was Re: -mm merge plans for 2.6.24)


On Wed, 3 Oct 2007, Nick Piggin wrote:
>
> I don't know if Linus actually disliked the patch itself, or disliked
> my (maybe confusingly worded) rationale?

Yes. I'd happily accept the patch, but I'd want it clarified and made
obvious what the problem was - and it wasn't the zero page itself, it was
a regression in the VM that made it less palatable.

I also thought that there were potentially better solutions, namely to
simply avoid the VM regression, but I also acknowledge that they may not
be worth it - I just want them to be on the table.

In short: the real cost of the zero page was the reference counting on the
page that we do these days. For example, I really do believe that the
problem could fairly easily be fixed by simply not considering zero_page
to be a "vm_normal_page()". We already *do* have support for pages not
getting ref-counted (since we need it for other things), and I think that
zero_page very naturally falls into exactly that situation.

So in many ways, I would think that turning zero-page into a nonrefcounted
page (the same way we really do have to do for other things anyway) would
be the much more *direct* solution, and in many ways the obvious one.

HOWEVER - if people think that it's easier to remove zero_page, and want
to do it for other reasons, *AND* can hopefully even back up the claim
that it never matters with numbers (ie that the extra pagefaults just make
the whole zero-page thing pointless), then I'd certainly accept the patch.

I'd just want the patch *description* to then also be correct, and blame
the right situation, instead of blaming zero-page itself.

Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-10-03 17:25    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site