> > On Wed, Jul 27, 2016 at 05:33:01PM +0000, Ananyev, Konstantin wrote: > > > > > > > -----Original Message----- > > > From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com] > > > Sent: Wednesday, July 27, 2016 6:11 PM > > > To: Thomas Monjalon <thomas.monjalon at 6wind.com> > > > Cc: Kulasek, TomaszX <tomaszx.kulasek at intel.com>; dev at dpdk.org; > > > Ananyev, Konstantin <konstantin.ananyev at intel.com> > > > Subject: Re: [dpdk-dev] [PATCH v2] doc: announce ABI change for > > > rte_eth_dev structure > > > > > > On Wed, Jul 27, 2016 at 01:59:01AM -0700, Thomas Monjalon wrote: > > > > > > Signed-off-by: Tomasz Kulasek <tomaszx.kulasek at intel.com> > > > > > > --- > > > > > > +* In 16.11 ABI changes are plained: the ``rte_eth_dev`` > > > > > > +structure will be > > > > > > + extended with new function pointer ``tx_pkt_prep`` allowing > > > > > > +verification > > > > > > + and processing of packet burst to meet HW specific > > > > > > +requirements before > > > > > > + transmit. Also new fields will be added to the > > > > > > ``rte_eth_desc_lim`` structure: > > > > > > + ``nb_seg_max`` and ``nb_mtu_seg_max`` provideing > > > > > > +information about number of > > > > > > + segments limit to be transmitted by device for TSO/non-TSO > > > > > > packets. > > > > > > > > > > Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com> > > > > > > > > I think I understand you want to split the TX processing: > > > > 1/ modify/write in mbufs > > > > 2/ write in HW > > > > and let application decide: > > > > - where the TX prep is done (which core) > > > > > > In what basics applications knows when and where to call tx_pkt_prep in > > > fast path. > > > if all the time it needs to call before tx_burst then the PMD won't > > > have/don't need this callback waste cycles in fast path.Is this the > > > expected behavior ? > > > Anything think it as compile time to make other PMDs wont suffer because > > > of this change. > > > > Not sure what suffering you are talking about... > > Current model - i.e. when application does preparations (or doesn't if > > none is required) on its own and just call tx_burst() would still be there. > > If the app doesn't want to use tx_prep() by some reason - that still > > ok, and decision is up to the particular app. > > So my question is in what basics application decides to call the preparation. > Can you tell me the use case in application perspective?
I suppose one most common use-case when application uses HW TX offloads, and don't' to cope on its own which L3/L4 header fields need to be filled for that particular dev_type/hw_offload combination. Instead it just setups the ol_flags, fills tx_offload fields and calls tx_prep(). Please read the original Tomasz's patch, I think he explained possible use-cases with lot of details. > and what if the PMD does not implement that callback then it is of waste > cycles. Right? If you refer as lost cycles here something like: RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->tx_prep, -ENOTSUP); then yes. Though comparing to actual work need to be done for most HW TX offloads, I think it is neglectable. Again, as I said before, it is totally voluntary for the application. Konstantin > > Jerin > > > > Konstantin > > > > > > > > > > > > - what to do if the TX prep fail > > > > So adding some processing in this first part becomes "not too > > > > expensive" or "manageable" from the application point of view. > > > > > > > > If I well understand the intent, > > > > > > > > Acked-by: Thomas Monjalon <thomas.monjalon at 6wind.com> (except > > > > typos ;)
