Re: [Qemu-block] [Qemu-devel] [RFC PATCH 00/40] Sneak peek of virtio and dataplane changes for 2.6

[Christian Borntraeger]

On 11/26/2015 10:36 AM, Christian Borntraeger wrote:
> On 11/24/2015 07:00 PM, Paolo Bonzini wrote:
>> This large series is basically all that I would like to get into 2.6.
>> It is a combination of several pieces of work on dataplane and
>> multithreaded block layer.
>>
>> It's also a large part of why I would like someone else to look at
>> miscellaneous patches for a while (in case you've missed that).  I
>> can foresee that following the reviews is going to be a huge time drain.
>>
>> With it I can get ~1300 Kiops on 8 disks (which I achieve with 2 iothreads
>> and 5 VCPUs).  The bulk of the improvement actually comes from the first
>> 8 patches, but the rest of the series is what prepares for what's next
>> to come in QEMU 2.7 and later, such as a multiqueue block layer.
>>
>> It's tedious to review, with some pretty large patches (3, 32, 33, 35).
> On 11/24/2015 07:00 PM, Paolo Bonzini wrote:
>> This large series is basically all that I would like to get into 2.6.
>> It is a combination of several pieces of work on dataplane and
>> multithreaded block layer.
>>
>> It's also a large part of why I would like someone else to look at
>> miscellaneous patches for a while (in case you've missed that).  I
>> can foresee that following the reviews is going to be a huge time drain.
>>
>> With it I can get ~1300 Kiops on 8 disks (which I achieve with 2 iothreads
>> and 5 VCPUs).  The bulk of the improvement actually comes from the first
>> 8 patches, but the rest of the series is what prepares for what's next
>> to come in QEMU 2.7 and later, such as a multiqueue block layer.
> 
> For some unknown reason, this seems to be slightly slower than 2.5-rc1 on my
> old z196. (have not net tested the z13)
> 
> your branch is certainly better regarding malloc, but worse regarding others.

Using the first 8 patches or so (commit be2f6b163e2b2a604f52a258fd932142c5974ffe
    vring: slim down allocation of VirtQueueElements)
is slightly faster than 2.5.0-rc1, so the regression seems to come from some
of the later patches.