linux-kernel - Re: [patch 1/2] x86_64 page fault NMI-safe

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Message-ID: <4C692129.4040307@redhat.com>
Date:	Mon, 16 Aug 2010 14:29:45 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Christoph Hellwig <hch@....de>, Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Tom Zanussi <tzanussi@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, Tejun Heo <htejun@...il.com>
Subject: Re: [patch 1/2] x86_64 page fault NMI-safe

  On 08/15/2010 09:31 PM, Mathieu Desnoyers wrote:
>
> I tested it in the past, and must admit that I changed from a vmalloc-based
> implementation to page-based using software cross-page write primitives based on
> feedback from Steven and Ingo. Diminishing TLB trashing seemed like a good
> approach, and using vmalloc on 32-bit machines is a pain, because users have to
> tweak the vmalloc region size at boot. So all in all, I moved to a vmalloc-less
> implementation without much more thought.


Forgot to comment about the i386 issue - that really is a blocker if you 
absolutely need to support large trace buffers on 32-bit machines.  I 
would urge all those people to move to x86_64 and be done with it, but I 
don't know all the use cases.

It's possible to hack this to work by having a private mm_struct and 
switching to it temporarily, but it will be horribly slow.

-- 
error compiling committee.c: too many arguments to function

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