Re: [patch 05/11] syslets: core code

[Evgeniy Polyakov]

On Wed, Feb 14, 2007 at 10:46:29AM +0100, Ingo Molnar (mingo@xxxxxxx) wrote:
> 
> * Evgeniy Polyakov <johnpol@xxxxxxxxxxx> wrote:
> 
> > This will end up badly - I used the same approach in the early kevent 
> > days and was proven to have swapable memory for the ring. I think it 
> > would be much better to have userspace allocated ring and use 
> > copy_to_user() there.
> 
> it is a userspace allocated ring - but pinned down by the kernel.

That's a problem - 1000/512 pages per 'usual' thread ends up with the
whole memory locked by malicious/stupid application (at least on Debian
and Mandrake there is no locked memory limit by default). And if such 
a limit exists, this will hurt big-iron applications, which want to used
high-order rings legitimely.

> 	Ingo

-- 
	Evgeniy Polyakov
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