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Date: Thu, 25 Mar 2010 11:58:30 +0200
From: Avi Kivity <avi@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH v3 1/1] Shared memory uio_pci driver
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Cam Macdonell <cam@cs.ualberta.ca>, qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org

On 03/25/2010 11:44 AM, Michael S. Tsirkin wrote:
> On Thu, Mar 25, 2010 at 11:40:09AM +0200, Avi Kivity wrote:
>    
>> On 03/25/2010 11:15 AM, Michael S. Tsirkin wrote:
>>      
>>> - Why are you using 32 bit long memory accesses for interrupts?
>>>     16 bit IO eould be enough and it's faster. This what virtio-pci does.
>>>
>>>
>>>        
>> Why is 16 bit io faster?
>>      
> Something to do with need for emulation to get address/data
> for pci memory accesses?
>    

pio is definitely faster than mmio (all that is needed is to set one bit 
on the BAR).  But 32 vs. 16 makes no difference.

-- 
error compiling committee.c: too many arguments to function