lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 6 Feb 2014 06:42:09 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ning Qu <quning@...gle.com>
Subject: Re: [RFC] de-asmify the x86-64 system call slowpath


* Linus Torvalds <torvalds@...ux-foundation.org> 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 (or, for anonymous pages, 
> by just optimistically trying to do an order-3 page allocation, and 
> if that works, just map the 32kB allocation you got as eight 
> individual pages).
> 
> I know it's been discussed at some point, and I even have a dim 
> memory of having seen some really ugly patches.

I have a dim memory of having written such group-prefaulting patches 
myself a decade ago or so - IIRC the main problem was that at that 
time we never found a common load where it really mattered, and it was 
easy to spend more time doing all this extra work and not see the 
prefaulted pages used.

But the cost/benefit balance has indeed changed so IMO it's worth a 
try.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists