Re: RFC: FreeBSD I/OAT driver

On 8/30/06, Andrew Gallatin <gallatin@xxxxxxxxxxx> wrote:


Excellent! Can you share some of these results? I would love to try
it, but I don't have FreeBSD on any machine with I/OAT hardware.

Prafulla had the results <nudges Prafulla>

I've taken a very quick look at it. Maybe I'm just being dense,
but I don't like the name "dma_" being in the global namespace.
Maybe things (like dma_*_list should be called at least
dmaengine_*_list, etc.

I have no commitment to specifics in the namespace, so it can be
changed to suit tastes.

There are some style(9) defects which I'm sure others who are more
proficient at style(9) than I am will point out (// comments, function
names not starting in column 0, etc).

Same as above, minor things we can fix...

How deep would you expect so->dma_wait_queue to get? Would it make
sense to keep a pointer to the last item so that insertion is O(1),
rather than O(N)?

Again, this is Prafulla's code, he should respond.

Would it be possible to have a sysctl tunable threshold, below which
the system does a normal uiomove? A normal copyout() will certainly
be faster at some point..

This sounds like a good idea. We only provided the stack client, because
of interest by a specific customer, but there is potential for this engine to
be used in a variety of places, for instance in VM.

For more diverse usages the registration/client code would need to be
enhanced, something like what Linux has now. That is doable later
down the path...

Thanks for the great work!

Drew

Thanks for looking it over :)

Jack
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