Re: [dpdk-dev] [PATCH] net/i40e: fix Tx fn selection when using new ethdev offloads

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: Richardson, Bruce
> Sent: Tuesday, May 1, 2018 2:53 PM
> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> Cc: Xing, Beilei <beilei.xing@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>; dev@dpdk.org; Yigit, Ferruh <ferruh.yigit@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] net/i40e: fix Tx fn selection when using new ethdev offloads
> 
> On Tue, May 01, 2018 at 02:24:39PM +0100, Ananyev, Konstantin wrote:
> > Hi Bruce,
> >
> > >
> > > The Tx function selection code in the driver only used the older txq
> > > flags values to check whether the scalar or vector functions should be
> > > used. This caused performance regressions with testpmd io-fwd as the
> > > scalar path rather than the vector one was being used in the default
> > > case. Fix this by changing the code to take account of new offloads and
> > > deleting the defines used for the old ones.
> > >
> > > Fixes: 7497d3e2f777 ("net/i40e: convert to new Tx offloads API")
> > >
> > > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > > ---
> > >  drivers/net/i40e/i40e_rxtx.c | 45 +++++++++++++++++++++++---------------------
> > >  1 file changed, 24 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
> > > index ec1ce54ca..c523af575 100644
> > > --- a/drivers/net/i40e/i40e_rxtx.c
> > > +++ b/drivers/net/i40e/i40e_rxtx.c
> > > @@ -40,9 +40,6 @@
> > >  /* Base address of the HW descriptor ring should be 128B aligned. */
> > >  #define I40E_RING_BASE_ALIGN	128
> > >
> > > -#define I40E_SIMPLE_FLAGS ((uint32_t)ETH_TXQ_FLAGS_NOMULTSEGS | \
> > > -					ETH_TXQ_FLAGS_NOOFFLOADS)
> > > -
> > >  #define I40E_TXD_CMD (I40E_TX_DESC_CMD_EOP | I40E_TX_DESC_CMD_RS)
> > >
> > >  #ifdef RTE_LIBRTE_IEEE1588
> > > @@ -70,6 +67,12 @@
> > >  #define I40E_TX_OFFLOAD_NOTSUP_MASK \
> > >  		(PKT_TX_OFFLOAD_MASK ^ I40E_TX_OFFLOAD_MASK)
> > >
> > > +static const uint64_t i40e_simple_ol_mask = (DEV_TX_OFFLOAD_MULTI_SEGS |
> > > +		DEV_TX_OFFLOAD_VLAN_INSERT |
> > > +		DEV_TX_OFFLOAD_SCTP_CKSUM |
> > > +		DEV_TX_OFFLOAD_UDP_CKSUM |
> > > +		DEV_TX_OFFLOAD_TCP_CKSUM);
> > > +
> >
> > Seems incomplete.
> > From i40e_ethdev.c full-featured tx supports:
> > dev_info->tx_offload_capa =
> >                 DEV_TX_OFFLOAD_VLAN_INSERT |
> >                 DEV_TX_OFFLOAD_QINQ_INSERT |
> >                 DEV_TX_OFFLOAD_IPV4_CKSUM |
> >                 DEV_TX_OFFLOAD_UDP_CKSUM |
> >                 DEV_TX_OFFLOAD_TCP_CKSUM |
> >                 DEV_TX_OFFLOAD_SCTP_CKSUM |
> >                 DEV_TX_OFFLOAD_OUTER_IPV4_CKSUM |
> >                 DEV_TX_OFFLOAD_TCP_TSO |
> >                 DEV_TX_OFFLOAD_VXLAN_TNL_TSO |
> >                 DEV_TX_OFFLOAD_GRE_TNL_TSO |
> >                 DEV_TX_OFFLOAD_IPIP_TNL_TSO |
> >                 DEV_TX_OFFLOAD_GENEVE_TNL_TSO;
> >
> > So we probably need the same here plus multiseg.
> > BTW, it is really strange that we don't have multiseg in tx_offload_capa.
> > Should be present I think.
> > Might be worse to create a new define for it, or just use dev_info->tx_offload_capa directly.
> > Konstantin
> >
> Thinking about this more, it seems that right now we don't need a masks at
> all. Any bits set in the offloads is going to cause us to use the scalar
> path or to error out with an invalid offload requested. Yes, it's not
> future-proofed in that it will need to be changed if we do end up
> supporting some offloads with the vector path in future, but then the same
> problem would occur if we just re-use the advertised capabilities too, like
> you suggest.
> 
> Therefore I think for V2 we'll just check for a non-zero offloads value.

Ok by me.
Konstantin