Re: Google Summer of Code

On Tue, Mar 05, 2013 at 03:15:12PM +0530, Mohit Dhingra wrote:
>*Hi Venkatesh,*
>
>Thanks a lot for a nice explanatory mail!
>
>I found the second project quite interesting, just to repeat  --
>** virtio-blk currently 'kicks' the host VMM directly from its
>   strategy() routine; it may make sense to defer this to a taskqueue. This
>   is a tiny change, but understanding the performance implications may
>   take a bit longer.
>
>As per my understanding, the notification to host through kick() involves
>the exit of the guest (as per attached paper). Hence, the aim for this
>project would also be to minimize the exits, or rather instantaneous exits.
>Deferring it to the task queue should definitely help. Other things that
>can be done in this project is batching of the buffers before kick() and
>dynamically deciding how many buffers can be batched together.
>
>Also, not all of the times deferring the 'kick' to taskqueue might not be a
>good idea. Finding those scenarios would be interesting where it helps, and
>where it is merely an overhead.

Yep, your understanding is correct. 

QEMU and friends generally try to handle batches of requests per-VMexit, 
so sometimes (often) there are wins to deferred 'kicks'. 

On Mon, Mar 11, 2013 at 09:42:08PM +0530, Mohit Dhingra wrote:
>   Hi Venkatesh,
>   Will you be able to mentor this project? I actually wanted to get
>   some
>   more info and hands on before applying for GSoC project. Please also
>   check
>   the previous mail and my proposal.

I'd be happy to mentor a project to work on performance of DFly under
virtualization (KVM or w/e), but this alone would be too small for a
full GSoC project, I think. Working on a few of the aspects I mentioned
earlier (or anything you come up with! very strongly encouraged!) would
be a better fit for a full project.
  
Take care,
-- vs;