Re: Binary Windows guest drivers are released

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On 09/25/2009 12:07 AM, Dor Laor wrote:
> On 09/24/2009 11:59 PM, Javier Guerra wrote:
>> On Thu, Sep 24, 2009 at 3:38 PM, Kenni Lund<kenni@kelu.dk>  wrote:
>>> I've done some benchmarking with the drivers on Windows XP SP3 32bit,
>>> but it seems like using the VirtIO drivers are slower than the IDE 
>>> drivers in
>>> (almost) all cases. Perhaps I've missed something or does the driver 
>>> still
>>> need optimization?
>>
>> very interesting!
>>
>> it seems that IDE wins on all the performance numbers, but VirtIO
>> always has lower CPU utilization.  i guess this is guest CPU %, right?
>> it would also be interesting to compare the CPU usage from the host
>> point of view, since a lower 'off-guest' CPU usage is very important
>> for scaling to many guests doing I/O.
>>
>
> Can you re-try it with setting the host ioscheduler to deadline?
> Virtio backend (thread pool) is sensitive for it.
>
> These drivers are mainly tweaked for win2k3 and win2k8. We once had 
> queue depth settings in the driver, not sure we still have it, Vadim, 
> can you add more info?
>
> Also virtio should provide IO parallelism as opposed to IDE. I don't 
> think your test test it. Virtio can provide more virtual drives than 
> the max 4 that ide offers.
>
> Dor
Windows XP 32-bit virtio block driver was created from our mainline code 
almost for fun.
Not like our mainline code, which is STORPORT oriented, it is a SCSIPORT 
(!!!!) mini-port driver.
SCSIPORT has never been known as I/O optimized storage stack.
SCSIPORT architecture is almost dead officially.
Windows XP 32-bit has no support for STORPORT or virtual storage stack.
Developing monolithic disk driver, which will sit right on top of 
virtio-blk PCI device, looks like the one way
to have some kind of high throughput storage for Windows XP 32-bit.

Regards,
Vadim.