linux-kernel - Re: [RFC] Reverting NUMA-affine page table allocation

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Message-ID: <20110302170702.GS3319@htj.dyndns.org>
Date:	Wed, 2 Mar 2011 18:07:02 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] Reverting NUMA-affine page table allocation

Hello,

On Wed, Mar 02, 2011 at 08:47:54AM -0800, Yinghai Lu wrote:
> > > Yeah, it's a pretty interesting piece of code in need of some cleanup.
> No, i mean second one is not causing any problem.
> 
> that only take end is intentionally. that will make sure we can get
> space for page table even in extreme case.

Hmmm... it seems like it only took @end because it always allocated
the whole page table in one go.  Always from the bottom to top.  Am I
missing something?

> > > If you're interested in doing the above, please go ahead and let me
> > > know.
> 
> No. please don't revert it.
> 
> Ingo, please get patches that will align to 1G ... from
> 
> 	git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-2.6-yinghai.git memblock

If you were gonna do that, you could have just said that you objected
to the reverting.  The message was Request for Comments - soliciting
responses.

As I wrote multiple times, I think the code as implemented is a bit
heavy handed for the problem.  And a bigger problem for me is that it
kind of just piles on the existing messiness and worsens it.  I really
hope we wouldn't be doing that anymore.

I tried to clean up the page table allocation code but the necessary
changes felt a bit too large at this stage, so IMO that's best left to
the next cycle.

To me, it seems complicated for not good enough reasons.  I'll defer
the decision to x86 maintainers.  Ingo, hpa, Thomas, what do you guys
think?

Thanks.

-- 
tejun
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