From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Cc: Thomas Monjalon <thomas.monjalon@6wind.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2] doc: announce ABI change for rte_eth_dev structure
Date: Wed, 27 Jul 2016 20:51:09 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725836B88894@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <20160727174133.GA22895@localhost.localdomain>
>
> On Wed, Jul 27, 2016 at 05:33:01PM +0000, Ananyev, Konstantin wrote:
> >
> >
> > > -----Original Message-----
> > > From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
> > > Sent: Wednesday, July 27, 2016 6:11 PM
> > > To: Thomas Monjalon <thomas.monjalon@6wind.com>
> > > Cc: Kulasek, TomaszX <tomaszx.kulasek@intel.com>; dev@dpdk.org;
> > > Ananyev, Konstantin <konstantin.ananyev@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@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@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@6wind.com> (except
> > > > typos ;)
next prev parent reply other threads:[~2016-07-27 20:51 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-20 14:24 [dpdk-dev] [PATCH] " Tomasz Kulasek
2016-07-20 15:01 ` Thomas Monjalon
2016-07-20 15:13 ` Ananyev, Konstantin
2016-07-20 15:22 ` Thomas Monjalon
2016-07-20 15:42 ` Kulasek, TomaszX
2016-07-21 15:24 ` [dpdk-dev] [PATCH v2] " Tomasz Kulasek
2016-07-21 22:48 ` Ananyev, Konstantin
2016-07-27 8:59 ` Thomas Monjalon
2016-07-27 17:10 ` Jerin Jacob
2016-07-27 17:33 ` Ananyev, Konstantin
2016-07-27 17:41 ` Jerin Jacob
2016-07-27 20:51 ` Ananyev, Konstantin [this message]
2016-07-28 2:13 ` Jerin Jacob
2016-07-28 10:36 ` Ananyev, Konstantin
2016-07-28 11:38 ` Jerin Jacob
2016-07-28 12:07 ` Avi Kivity
2016-07-28 13:01 ` Ananyev, Konstantin
2016-07-28 13:58 ` Olivier MATZ
2016-07-28 14:21 ` Ananyev, Konstantin
2016-07-28 13:59 ` Jerin Jacob
2016-07-28 14:52 ` Thomas Monjalon
2016-07-28 16:25 ` Jerin Jacob
2016-07-28 17:07 ` Thomas Monjalon
2016-07-31 7:50 ` Vlad Zolotarov
2016-07-28 12:04 ` Avi Kivity
2016-07-31 7:46 ` [dpdk-dev] [PATCH] " Vlad Zolotarov
2016-07-31 8:10 ` Vlad Zolotarov
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