[dpdk-dev] Is vhost vring_avail size tunable?

[dpdk-dev] Is vhost vring_avail size tunable?

[Tim Deng]

Hi,

Under heavy work load, I found there were some packet lost caused by
"Failed to get enough desc from vring...", is there any way to get the
vring size larger?

Thanks,
Tim

Re: [dpdk-dev] Is vhost vring_avail size tunable?

[Ouyang, Changchun]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Tim Deng
> Sent: Sunday, June 7, 2015 4:02 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] Is vhost vring_avail size tunable?
> 
> 
> Hi,
> 
> Under heavy work load, I found there were some packet lost caused by
> "Failed to get enough desc from vring...", is there any way to get the vring
> size larger?
> 

Qemu has hard code to set the vring size as 256, you need change the value to a bigger one if you want to enlarge it.

Thanks
Changchun

Re: [dpdk-dev] Is vhost vring_avail size tunable?

[Tim Deng]

Thank you Changchun!

Tim

在 2015-06-08 09:56:43，"Ouyang, Changchun" <changchun.ouyang@intel.com> 写道：
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Tim Deng
>> Sent: Sunday, June 7, 2015 4:02 PM
>> To: dev@dpdk.org
>> Subject: [dpdk-dev] Is vhost vring_avail size tunable?
>> 
>> 
>> Hi,
>> 
>> Under heavy work load, I found there were some packet lost caused by
>> "Failed to get enough desc from vring...", is there any way to get the vring
>> size larger?
>> 
>
>Qemu has hard code to set the vring size as 256, you need change the value to a bigger one if you want to enlarge it.
>
>Thanks
>Changchun
>

Re: [dpdk-dev] Is vhost vring_avail size tunable?

[Stephen Hemminger]

On Sun, 7 Jun 2015 16:02:04 +0800 (CST)
"Tim Deng" <dpdkdev@126.com> wrote:

> 
> Hi,
> 
> Under heavy work load, I found there were some packet lost caused by
> "Failed to get enough desc from vring...", is there any way to get the
> vring size larger?
> 
> Thanks,
> Tim

One thing that could help the DPDK virtio driver would be to support
INDIRECT descriptors. By using that, it is possible to get 256 packets
into the 256 slots in QEMU.  Currently half the slots are taken by
headers.

The implementation of vhost driver likewise needs to get support
for INDIRECT descriptors and some other features in order to use slots
more efficiently.