Re: VKernel progress update - 8 Jan 2006 (milestone reached!)

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

Matthew Dillon wrote:
> :how about using O_ASYNC and SIGIO for console and network, etc?
> :
> :we could build a device tree (starting with a nexus), where drivers could register filedescs as "interrupt" resources.  or something like that...
>     It would work, but it wouldn't be fun.  Signals are very expensive.  Very
>     very expensive.
>
>     Kqueue or select for the network would work, the provisio being that 
>     I would need to create some sort of mechanism to break out of an
>     emulated user context based on a kqueue event occuring.  I don't think
>     that would be too hard to do.

Okay, but I guess no other subsystem would benefit from this.  However, how do you manage to "break out"?  You'd have to have some kind of context switching, right?

>     Second, we need some sort of 
>     pseudo-DMA to handle the transfer... maybe a kernel thread.  We have
>     the advantage that the transfers to and from the disk only occur
>     from the virtual kernel's 'memory' (which itself is just a memory mapped
>     file), so it would be fairly easy to write a real-kernel kernel thread
>     to help out there.

I think that's called aio and is even in POSIX.  I think aio should be pursued further, just the implementation could need some polishing.

cheers
 simon

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