linux-kernel - Re: [PATCH] kmemcheck: SMP support

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Message-ID: <483A8310.6030309@qumranet.com>
Date:	Mon, 26 May 2008 12:29:52 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, Pekka Paalanen <pq@....fi>
Subject: Re: [PATCH] kmemcheck: SMP support

Vegard Nossum wrote:
> On Fri, May 23, 2008 at 5:06 PM, Ingo Molnar <mingo@...e.hu> wrote:
>   
>> Vegard, wanna have a look at introducing per CPU kernel pagetables? I
>> tried that once in the past and it wasnt too horrible. (the patches are
>> gone though) We could do it before bringing other CPUs online, i.e. much
>> of the really yucky boot time pagetable juggling phase would be over
>> already. Hm?
>>     
>
> Ingo.
>
> It really doesn't matter how easy it was for you.
>
> You're one of the x86 maintainers.
>
> And I think you're forgetting how hard these things are for a newbie.
> I don't even know which one comes first of pmds and puds.
>
> Per-cpu page tables sounds about on the same scale of as, say,
> rewriting the VM or some other major subsystem. Epic!
>
>   

You might be able to pull off a simple implementation using 
paravirt_ops, without impacting the core VM.

Basically, you keep the current global pagetables, but never set them as 
real pagetables.  Instead you keep per-cpu copies of these pagetables 
and sync them from the master pagetable as needed.

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

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