[dpdk-dev] [PATCH v12 0/6] add Tx preparation

[Ananyev, Konstantin]

Hi John,

> 
> Hi,
> -john
> 
> > -----Original Message-----
> > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> > Sent: Monday, November 28, 2016 3:03 AM
> > To: dev at dpdk.org; Rahul Lakkireddy <rahul.lakkireddy at chelsio.com>;
> > Stephen Hurd <stephen.hurd at broadcom.com>; Jan Medala
> > <jan at semihalf.com>; Jakub Palider <jpa at semihalf.com>; John Daley
> > (johndale) <johndale at cisco.com>; Adrien Mazarguil
> > <adrien.mazarguil at 6wind.com>; Alejandro Lucero
> > <alejandro.lucero at netronome.com>; Harish Patil
> > <harish.patil at qlogic.com>; Rasesh Mody <rasesh.mody at qlogic.com>; Jerin
> > Jacob <jerin.jacob at caviumnetworks.com>; Yuanhan Liu
> > <yuanhan.liu at linux.intel.com>; Yong Wang <yongwang at vmware.com>
> > Cc: Tomasz Kulasek <tomaszx.kulasek at intel.com>;
> > konstantin.ananyev at intel.com; olivier.matz at 6wind.com
> > Subject: Re: [dpdk-dev] [PATCH v12 0/6] add Tx preparation
> >
> > We need attention of every PMD developers on this thread.
> >
> > Reminder of what Konstantin suggested:
> > "
> > - if the PMD supports TX offloads AND
> > - if to be able use any of these offloads the upper layer SW would have to:
> >     * modify the contents of the packet OR
> >     * obey HW specific restrictions
> > then it is a PMD developer responsibility to provide tx_prep() that would
> > implement expected modifications of the packet contents and restriction
> > checks.
> > Otherwise, tx_prep() implementation is not required and can be safely set to
> > NULL.
> > "
> >
> > I copy/paste also my previous conclusion:
> >
> > Before txprep, there is only one API: the application must prepare the
> > packets checksum itself (get_psd_sum in testpmd).
> > With txprep, the application have 2 choices: keep doing the job itself or call
> > txprep which calls a PMD-specific function.
> > The question is: does non-Intel drivers need a checksum preparation for
> > TSO?
> > Will it behave well if txprep does nothing in these drivers?
> >
> > When looking at the code, most of drivers handle the TSO flags.
> > But it is hard to know whether they rely on the pseudo checksum or not.
> >
> > git grep -l 'PKT_TX_UDP_CKSUM\|PKT_TX_TCP_CKSUM\|PKT_TX_TCP_SEG'
> > drivers/net/
> >
> > drivers/net/bnxt/bnxt_txr.c
> > drivers/net/cxgbe/sge.c
> > drivers/net/e1000/em_rxtx.c
> > drivers/net/e1000/igb_rxtx.c
> > drivers/net/ena/ena_ethdev.c
> > drivers/net/enic/enic_rxtx.c
> > drivers/net/fm10k/fm10k_rxtx.c
> > drivers/net/i40e/i40e_rxtx.c
> > drivers/net/ixgbe/ixgbe_rxtx.c
> > drivers/net/mlx4/mlx4.c
> > drivers/net/mlx5/mlx5_rxtx.c
> > drivers/net/nfp/nfp_net.c
> > drivers/net/qede/qede_rxtx.c
> > drivers/net/thunderx/nicvf_rxtx.c
> > drivers/net/virtio/virtio_rxtx.c
> > drivers/net/vmxnet3/vmxnet3_rxtx.c
> >
> > Please, we need a comment for each driver saying "it is OK, we do not need
> > any checksum preparation for TSO"
> > or
> > "yes we have to implement tx_prepare or TSO will not work in this mode"
> 
> I like the idea of tx prep since it should make for cleaner apps.
> 
> For enic, I believe the answer is " it is OK, we do not need any checksum preparation".
> 
> Prior to now, it was necessary to set IP checksum to 0 and put in a TCP/UDP pseudo header. But there is a hardware overwrite of
> checksums option which makes preparation in software unnecessary and it is testing out well so far. I plan to enable it in 17.02. TSO is also
> being enabled for 17.02 and it does not look like any prep is required. So I'm going with " txprep NULL pointer is OK for enic", but may have
> to change my mind if something comes up in testing.

That's great thanks.
Other non-Intel PMD maintainers, please any feedback? 
Konstantin

> 
> -john