linux-kernel - Re: Why preallocate pmd in x86 32-bit PAE?

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Message-Id: <200711161653.00824.ak@suse.de>
Date:	Fri, 16 Nov 2007 16:53:00 +0100
From:	Andi Kleen <ak@...e.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	William Lee Irwin III <wli@...omorphy.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Why preallocate pmd in x86 32-bit PAE?

On Friday 16 November 2007 16:45:16 H. Peter Anvin wrote:
> Andi Kleen wrote:
> >> I think Jeremy's question was due to trying to reduce the 32/64-bit 
> >> differences.  Performance-wise, it might add a small amount to user 
> >> setup time (a typical 32-bit process will need all four, for the main 
> >> binary, libraries, stack and kernel, respectively) 
> > 
> > With the new top down mmap layout and standard 3:1 split it should typically 
> > only need two.
> > 
> 
> Well, three with the kernel.

I didn't count kernel because it is always fixed anyways and about zero
overhead for the normal setup case.

-Andi

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