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Re: [Qemu-block] [Qemu-devel] [RFC PATCH 00/40] Sneak peek of virtio and


From: Christian Borntraeger
Subject: Re: [Qemu-block] [Qemu-devel] [RFC PATCH 00/40] Sneak peek of virtio and dataplane changes for 2.6
Date: Wed, 16 Dec 2015 15:40:06 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0

On 12/16/2015 01:54 PM, Christian Borntraeger wrote:
> On 12/09/2015 09:35 PM, Paolo Bonzini wrote:
>>
>>
>> On 26/11/2015 11:39, Paolo Bonzini wrote:
>>> I would really prefer to get rid of vring.c as soon as the infrastructure
>>> makes it possible---even if it's faster. We know what makes virtio.c
>>> slower, and it's simpler to fix virtio.c than to convert all the other
>>> models to vring.c _plus_ make vring.c safe for migration.
>>
>> I've now pushed some optimizations of exec.c to the same place (branch
>> dataplane, git://github.com/bonzini/qemu.git).  Basically if the length
>> of an address_space_read is constant, and the target ends up being RAM,
>> the compiler can inline address_space_read in the caller and in
>> particular eliminate the memcpy.
> 
> Just some quick remarks before I leave into vacation:
> 
> Performance seems to be better than the initial version. 

In fact, it seems to be faster than 2.5-rc4. At least with the one
single test case on null block devices that I run.






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