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Date:	Wed, 5 Feb 2014 20:33:27 -0800
From:	Linus Torvalds <>
To:	"Kirill A. Shutemov" <>
Cc:	Peter Anvin <>, Ingo Molnar <>,
	Thomas Gleixner <>,
	Peter Zijlstra <>,
	"the arch/x86 maintainers" <>,
	Linux Kernel Mailing List <>,
	Ning Qu <>
Subject: Re: [RFC] de-asmify the x86-64 system call slowpath

On Wed, Feb 5, 2014 at 6:32 PM, Linus Torvalds
<> wrote:
> No, I was thinking "try to optimistically map 8 adjacent aligned pages
> at a time" - that would be the same cacheline in the page tables, so
> it would be fairly cheap if we couple it with a gang-lookup of the
> pages in the page cache

Doing the gang-lookup is hard, since it's all abstracted away, but the
attached patch kind of tries to do what I described.

This patch probably doesn't work, but something *like* this might be
worth playing with.

Except I suspect the page-backed faults are actually the minority,
judging by how high clear_page_c_e is in the profile it's probably
mostly anonymous memory. I have no idea why I started with the (more
complex) case of file-backed prefaulting. Oh well.


View attachment "patch.diff" of type "text/plain" (1753 bytes)

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