From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: i40e queues per VF
Date: Wed, 08 Mar 2017 12:25:49 +0100
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Cc: "Zhang, Helin" <helin.zhang@intel.com>, "Mcnamara,
 John" <john.mcnamara@intel.com>, dev@dpdk.org, ferruh.yigit@intel.com
To: "Wu, Jingjing" <jingjing.wu@intel.com>
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ping - still waiting for answers to below questions, please

2017-02-16 15:55, Thomas Monjalon:
> 2017-02-16 13:58, Wu, Jingjing:
> > From: Thomas Monjalon
> > > 
> > > 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.
> 
> The description "Number of queues reserved for each SR-IOV VF" seems
> partially wrong. Please explain it is a queue pair.
> 
> > > 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.
> 
> If we can create 16 queue pairs, why restrict the default configuration to 4?
> Why is it a build-time config option?