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Fri, 28 Oct 2016 12:34:49 +0100
From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, Thomas Monjalon
<thomas.monjalon@6wind.com>
Thread-Topic: [dpdk-dev] [PATCH v11 1/6] ethdev: add Tx preparation
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Date: Fri, 28 Oct 2016 11:34:49 +0000
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Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v11 1/6] ethdev: add Tx preparation
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>=20
> Hi Thomasz,
>=20
> >
> > 2016-10-27 16:24, Ananyev, Konstantin:
> > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > > 2016-10-27 15:52, Ananyev, Konstantin:
> > > > > > Hi Tomasz,
> > > > > >
> > > > > > This is a major new function in the API and I still have some c=
omments.
> > > > > >
> > > > > > 2016-10-26 14:56, Tomasz Kulasek:
> > > > > > > --- a/config/common_base
> > > > > > > +++ b/config/common_base
> > > > > > > +CONFIG_RTE_ETHDEV_TX_PREP=3Dy
> > > > > >
> > > > > > We cannot enable it until it is implemented in every drivers.
> > > > >
> > > > > Not sure why?
> > > > > If tx_pkt_prep =3D=3D NULL, then rte_eth_tx_prep() would just act=
as noop.
> > > > > Right now it is not mandatory for the PMD to implement it.
> > > >
> > > > If it is not implemented, the application must do the preparation b=
y itself.
> > > > From patch 6:
> > > > "
> > > > Removed pseudo header calculation for udp/tcp/tso packets from
> > > > application and used Tx preparation API for packet preparation and
> > > > verification.
> > > > "
> > > > So how does it behave with other drivers?
> > >
> > > Hmm so it seems that we broke testpmd csumonly mode for non-intel dri=
vers..
> > > My bad, missed that part completely.
> > > Yes, then I suppose for now we'll need to support both (with and with=
out) code paths for testpmd.
> > > Probably a new fwd mode or just extra parameter for the existing one?
> > > Any other suggestions?
> >
> > Please think how we can use it in every applications.
> > It is not ready.
> > Either we introduce the API without enabling it, or we implement it
> > in every drivers.
>=20
> I understand your position here, but just like to point that:
> 1) It is a new functionality optional to use.
> The app is free not to use that functionality and still do the prepa=
ration itself
> (as it has to do it now).
> All existing apps would keep working as expected without using that f=
unction.
> Though if the app developer knows that for all HW models he plans to =
run on
> tx_prep is implemented - he is free to use it.
> 2) It would be difficult for Tomasz (and other Intel guys) to impleme=
nt tx_prep()
> for all non-Intel HW that DPDK supports right now.
> We just don't have all the actual HW in stock and probably adequate =
knowledge of it.
> So we depend here on the good will of other PMD mainaners/developers =
to implement
> tx_prep() for these devices.
> From other side, if it will be disabled by default, then, I think,
> PMD developers just wouldn't be motivated to implement it.
> So it will be left untested and unused forever.
Actually as another thought:
Can we have it enabled by default, but mark it as experimental or so?
If memory serves me right, we've done that for cryptodev in the past, no?
Konstantin
>=20
> >
> > > > > > > struct rte_eth_dev {
> > > > > > > eth_rx_burst_t rx_pkt_burst; /**< Pointer to PMD receive fu=
nction. */
> > > > > > > eth_tx_burst_t tx_pkt_burst; /**< Pointer to PMD transmit f=
unction. */
> > > > > > > + eth_tx_prep_t tx_pkt_prep; /**< Pointer to PMD transmit pre=
pare function. */
> > > > > > > struct rte_eth_dev_data *data; /**< Pointer to device data=
*/
> > > > > > > const struct eth_driver *driver;/**< Driver for this device=
*/
> > > > > > > const struct eth_dev_ops *dev_ops; /**< Functions exported =
by PMD */
> > > > > >
> > > > > > Could you confirm why tx_pkt_prep is not in dev_ops?
> > > > > > I guess we want to have several implementations?
> > > > >
> > > > > Yes, it depends on configuration options, same as tx_pkt_burst.
> > > > >
> > > > > >
> > > > > > Shouldn't we have a const struct control_dev_ops and a struct d=
atapath_dev_ops?
> > > > >
> > > > > That's probably a good idea, but I suppose it is out of scope for=
that patch.
> > > >
> > > > No it's not out of scope.
> > > > It answers to the question "why is it added in this structure and n=
ot dev_ops".
> > > > We won't do this change when nothing else is changed in the struct.
> > >
> > > Not sure I understood you here:
> > > Are you saying datapath_dev_ops/controlpath_dev_ops have to be introd=
uced as part of that patch?
> > > But that's a lot of changes all over rte_ethdev.[h,c].
> > > It definitely worse a separate patch (might be some discussion) for m=
e.
> >
> > Yes it could be a separate patch in the same patchset.
>=20
> Honestly, I think it is a good idea, but it is too late and too risky to =
do such change right now.
> We are on RC2 right now, just few days before RC3...
> Can't that wait till 17.02?
> From my understanding - it is pure code restructuring, without any functi=
onality affected.
> Konstantin
>=20