linux-kernel - Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory

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Message-ID: <20130625073122.GB11420@gmail.com>
Date:	Tue, 25 Jun 2013 09:31:22 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Nathan Zimmer <nzimmer@....com>, holt@....com, travis@....com,
	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	yinghai@...nel.org, akpm@...ux-foundation.org,
	gregkh@...uxfoundation.org, x86@...nel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory


* H. Peter Anvin <hpa@...or.com> wrote:

> On 06/24/2013 12:39 PM, Ingo Molnar wrote:
> > 
> > That might be a bit too granular: if we hit such an uninitialized block of 
> > memory we'd have to process 262,144 pages - potentially from an IRQ 
> > handler that does GFP_ATOMIC... or other latency critical code.
> > 
> > With 2MB we'd have to on-demand initialize 512 pages, which shouldn't show 
> > up during normal use.
> > 
> 
> No... you split the gigabyte page into 511 2M pages and 512 4K pages.

Oh, double deferred initialization. That should solve the 32 exabyte 
problem as well I guess ;-)

Thanks,

	Ingo
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