Re: [dpdk-dev] i40e queues per VF

["Wu, Jingjing" <jingjing.wu@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Tuesday, February 14, 2017 6:07 PM
> To: Zhang, Helin <helin.zhang@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>
> Cc: Mcnamara, John <john.mcnamara@intel.com>; dev@dpdk.org
> Subject: i40e queues per VF
> 
> Hi,
> 
> When reading the documentation, it is not easy to understand the capability of
> i40evf for the number of queues.
> 
> First, please could you explain why we need a build-time config option?
> In the doc, there is neither justification nor tuning guidelines:
> 
> http://dpdk.org/doc/guides/nics/i40e.html#config-file-options
> "
> CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_PF (default 64) Number of
> queues reserved for PF.
> CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_VF (default 4) Number of
> queues reserved for each SR-IOV VF.
> "

This number is used as initialization time to allocate queue number
for PF/VF for HW's queue pool. Will add more description in i40e.rst.
> 
> I feel these are hard limits and should be some constants in the code, not some
> build configuration options.
> 
> The other doc to look at is:
> http://dpdk.org/doc/guides/nics/intel_vf.html#intel-fortville-10-40-gigabit-
> ethernet-controller-vf-infrastructure
> "
> Each VF can have a maximum of 16 queue pairs.
> "
> 
> Do we agree that a queue pair is 1 Rx queue / 1 Tx queue?
> Note: the concept of queue pairs in Intel VF should be explained somewhere.
> 
Yes.
> Below, a different limitation is given:
> "
> The available queue number(at most 4) per VF depends on the total number of
> pool, which is determined by the max number of VF at PF initialization stage and
> the number of queue specified in config "
>
I think there may be some inconsistent description in  doc intel_vf.rst due to
Multiple kinds of NICs. We should correct them.
Thanks for pointing that.

> So what is the real maximum of queue pairs? 4 or 16?
> The datasheet talks about 16 queues. Is it 8 pairs?

That's is 16 queue pairs. 16 RX queues and 16 Tx queues.
> 
> Is there something to configure the number of queues when creating VF with the
> kernel driver?

In kernel driver, it seems at most only 4 queues are supported. That's
Why we add  build-time config option to make more queues are possible.


Thanks
Jingjing