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

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Message-ID: <51C8A728.8010409@zytor.com>
Date:	Mon, 24 Jun 2013 13:08:08 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>
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

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.

	-hpa


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