Re: [PATCH v2] virtio: increase virtuqueue size for virtio-scsi and virtio-blk

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

On 18.02.2020 16:59, Denis Plotnikov wrote:
>
>
> On 18.02.2020 16:53, Stefan Hajnoczi wrote:
>> On Thu, Feb 13, 2020 at 05:59:27PM +0300, Denis Plotnikov wrote:
>>> v1:
>>>    * seg_max default value changing removed
>>>
>>> ---
>>> The goal is to reduce the amount of requests issued by a guest on
>>> 1M reads/writes. This rises the performance up to 4% on that kind of
>>> disk access pattern.
>>>
>>> The maximum chunk size to be used for the guest disk accessing is
>>> limited with seg_max parameter, which represents the max amount of
>>> pices in the scatter-geather list in one guest disk request.
>>>
>>> Since seg_max is virqueue_size dependent, increasing the virtqueue
>>> size increases seg_max, which, in turn, increases the maximum size
>>> of data to be read/write from a guest disk.
>>>
>>> More details in the original problem statment:
>>> https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html
>>>
>>> Suggested-by: Denis V. Lunev <den@openvz.org>
>>> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
>>> ---
>>>   hw/block/virtio-blk.c | 2 +-
>>>   hw/core/machine.c     | 2 ++
>>>   hw/scsi/virtio-scsi.c | 2 +-
>>>   3 files changed, 4 insertions(+), 2 deletions(-)
>> I fixed up the "virtuqueue" typo in the commit message and the
>> mis-formatted commit description (git-am(1) stops including lines after
>> the first "---").
> Actually, I sent the corrected version v3 of the patch last week. But 
> it seems it got lost among that gigantic patch flow in the mailing 
> list :)
> Thanks for applying!
>
> Denis
>>
>> Thanks, applied to my block tree:
>> https://github.com/stefanha/qemu/commits/block
>>
>> Stefan
I'm going to send the test checking the virtqueue-sizes for machine 
types a little bit later.

Denis