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Date: Fri, 2 Nov 2001 05:12:12 +0000
From: Pavel Machek <pavel@suse.cz>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>,
       Benjamin LaHaise <bcrl@redhat.com>, Andrea Arcangeli <andrea@suse.de>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Chris Friesen <cfriesen@nortelnetworks.com>,
       Pavel Machek <pavel@Elf.ucw.cz>, linux-kernel@vger.kernel.org,
       linux-aio@kvack.org
Subject: Re: aio-core why not using SuS? [Re: [rfc] aio-core for 2.5.29 (Re: async-io API registration for 2.5.29)]
Message-ID: <20011102051212.H35@toy.ucw.cz>
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Hi!
> 
> But if you have such a mapping, then you _cannot_ make a per-task VM
> space, because many tasks will share the same VM. You cannot even do a
> per-cpu mapping change (and rewrite the VM on thread switch), since the VM
> is _shared_ across CPU's, and absolutely has to be in order to work with
> CPU's that do TLB fill in hardware (eg x86).

You could have different %cr3 on different CPUs and use page tables as TLBs
(emulating software-filled TLBs, basically); but that smells like "bye bye
performance".
								Pavel
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.

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