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Re: remove zero_page (was Re: -mm merge plans for 2.6.24)

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To: Linus Torvalds <torvalds@...>
Cc: Hugh Dickins <hugh@...>, Andrew Morton <akpm@...>, <linux-mm@...>, <linux-kernel@...>
Date: Tuesday, October 9, 2007 - 6:15 am

On Wednesday 10 October 2007 12:22, Linus Torvalds wrote:

I gave 2 other numbers. After that, it really doesn't matter if I give
you 2 numbers or 200, because it wouldn't change the fact that there
are 3 programs using the ZERO_PAGE that we'll never know about.



I think I've always admitted I'm handwaving in my assertion that programs
would not be using the zero page. My handwaving is an attempt to show that
I have some vaguely reasonable reasons to think it will be OK to remove it.
That's all.



Was the last one OK?



The dishonesty in the changelog is more of an oversight than an attempt
to get it merged. It never even crossed my mind that you would be fooled
by it ;) To prove my point: the *first* approach I posted to fix this
problem was exactly a patch to special-case the zero_page refcounting
which was removed with my PageReserved patch. Neither Hugh nor yourself
liked it one bit!

So I have no particular bias against the zero page or problem admitting
I introduced the issue. I do just think this could be a nice opportunity
to try getting rid of the zero page and simplifiy things.



Basically: I don't know what else to show you! I expect it would be
relatively difficult to find a measurable difference between no zero-page
and zero-page with no refcounting problem. Precisely because I can't
find anything that really makes use of it. Again: what numbers can I
get for you that would make you feel happier about it?

Anyway, before you change your mind: it's a deal! If somebody screams
then I'll have a patch for you to reintroduce the zero page minus
refcounting the next day.
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Messages in current thread:
-mm merge plans for 2.6.24, Andrew Morton, (Mon Oct 1, 5:22 pm)
new aops merge [was Re: -mm merge plans for 2.6.24], Hugh Dickins, (Tue Oct 2, 12:21 pm)
x86 patches was Re: -mm merge plans for 2.6.24, Andi Kleen, (Tue Oct 2, 2:18 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andrew Morton, (Tue Oct 2, 2:32 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Ingo Molnar, (Tue Oct 2, 3:37 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andi Kleen, (Tue Oct 2, 3:46 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Thomas Gleixner, (Tue Oct 2, 3:58 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andi Kleen, (Tue Oct 2, 3:01 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andy Whitcroft, (Tue Oct 2, 5:26 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andrew Morton, (Tue Oct 2, 3:18 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, KAMEZAWA Hiroyuki, (Tue Oct 2, 3:36 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Christoph Lameter, (Tue Oct 2, 2:16 pm)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Nish Aravamudan, (Tue Oct 2, 12:40 pm)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andrew Morton, (Tue Oct 2, 3:43 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, KAMEZAWA Hiroyuki, (Tue Oct 2, 4:16 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Christoph Lameter, (Tue Oct 2, 2:18 pm)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Yasunori Goto, (Tue Oct 2, 6:48 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Lee Schermerhorn, (Tue Oct 2, 1:25 pm)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Lee Schermerhorn, (Tue Oct 2, 1:17 pm)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Matt Mackall, (Tue Oct 2, 3:55 am)
Re: x86 patches was Re: -mm merge plans for 2.6.24, Andi Kleen, (Tue Oct 2, 3:59 am)
Re: -mm merge plans for 2.6.24, Pekka Enberg, (Tue Oct 2, 12:12 pm)
v4l-stk11xx* [Was: -mm merge plans for 2.6.24], Jiri Slaby, (Tue Oct 2, 3:59 am)
writeback fixes, Fengguang Wu, (Tue Oct 2, 4:39 am)
Re: -mm merge plans for 2.6.24, Borislav Petkov, (Sat Oct 13, 4:44 am)
Re: -mm merge plans for 2.6.24, Andrew Morton, (Sat Oct 13, 4:52 am)
Re: -mm merge plans for 2.6.24, Borislav Petkov, (Sat Oct 13, 7:45 am)
r/o bind mounts, was Re: -mm merge plans for 2.6.24, Christoph Hellwig, (Tue Oct 9, 5:19 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Wed Oct 3, 11:21 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Tue Oct 9, 10:52 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Tue Oct 9, 10:22 pm)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Nick Piggin, (Tue Oct 9, 6:15 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Hugh Dickins, (Wed Oct 10, 12:06 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Wed Oct 10, 1:20 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Wed Oct 10, 11:04 am)
Re: remove zero_page (was Re: -mm merge plans for 2.6.24), Linus Torvalds, (Tue Oct 9, 11:06 pm)
wibbling over the cpuset shed domain connnection, Paul Jackson, (Mon Oct 1, 5:34 pm)
Re: wibbling over the cpuset shed domain connnection, Nick Piggin, (Tue Oct 2, 8:36 am)
Re: wibbling over the cpuset shed domain connnection, Paul Jackson, (Wed Oct 3, 1:21 am)
Re: wibbling over the cpuset shed domain connnection, Nick Piggin, (Tue Oct 2, 9:12 am)
Re: wibbling over the cpuset shed domain connnection, Paul Jackson, (Wed Oct 3, 3:00 am)
Re: wibbling over the cpuset shed domain connnection, Andrew Morton, (Wed Oct 3, 6:57 am)
per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Tue Oct 2, 4:17 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Martin Knoblauch, (Wed Oct 3, 7:00 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Fri Oct 26, 10:48 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Trond Myklebust, (Fri Oct 26, 12:37 pm)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Fri Dec 14, 10:50 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Miklos Szeredi, (Fri Dec 14, 11:14 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Fri Dec 14, 11:54 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Miklos Szeredi, (Fri Oct 26, 11:06 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Fri Oct 26, 11:22 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Fri Oct 26, 11:33 am)
[PATCH] mm: sysfs: expose the BDI object in sysfs, Peter Zijlstra, (Fri Nov 2, 10:59 am)
Re: [PATCH] mm: sysfs: expose the BDI object in sysfs, Kay Sievers, (Fri Nov 2, 11:13 am)
Re: per BDI dirty limit (was Re: -mm merge plans for 2.6.24), Peter Zijlstra, (Sat Oct 27, 12:07 pm)
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