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

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

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