From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Rong, Leyi" <leyi.rong@intel.com>,
"Yigit, Ferruh" <ferruh.yigit@intel.com>,
"Zhang, Qi Z" <qi.z.zhang@intel.com>,
"Xing, Beilei" <beilei.xing@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] net/i40e: add Tx preparation for vector data path
Date: Thu, 8 Apr 2021 10:32:51 +0000 [thread overview]
Message-ID: <DM6PR11MB4491ABAA946C470A4AAB73539A749@DM6PR11MB4491.namprd11.prod.outlook.com> (raw)
In-Reply-To: <SN6PR11MB2621B5FB95D3DF6A7604C7EAEC749@SN6PR11MB2621.namprd11.prod.outlook.com>
>
> > -----Original Message-----
> > From: Yigit, Ferruh <ferruh.yigit@intel.com>
> > Sent: Thursday, April 8, 2021 12:40 AM
> > To: Rong, Leyi <leyi.rong@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>; Xing,
> > Beilei <beilei.xing@intel.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH] net/i40e: add Tx preparation for vector data
> > path
> >
> > On 3/31/2021 9:53 AM, Leyi Rong wrote:
> > > Fill up dev->tx_pkt_prepare to i40e_pkt_prepare when on vector and
> > > simple data path selection, as the sanity check is needed ideally.
> > >
> > > Signed-off-by: Leyi Rong <leyi.rong@intel.com>
> > > ---
> > > drivers/net/i40e/i40e_rxtx.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/i40e/i40e_rxtx.c
> > > b/drivers/net/i40e/i40e_rxtx.c index 61cb204be2..b3d7765e3b 100644
> > > --- a/drivers/net/i40e/i40e_rxtx.c
> > > +++ b/drivers/net/i40e/i40e_rxtx.c
> > > @@ -3412,7 +3412,7 @@ i40e_set_tx_function(struct rte_eth_dev *dev)
> > > PMD_INIT_LOG(DEBUG, "Simple tx finally be used.");
> > > dev->tx_pkt_burst = i40e_xmit_pkts_simple;
> > > }
> > > - dev->tx_pkt_prepare = NULL;
> > > + dev->tx_pkt_prepare = i40e_prep_pkts;
> > > } else {
> > > PMD_INIT_LOG(DEBUG, "Xmit tx finally be used.");
> > > dev->tx_pkt_burst = i40e_xmit_pkts;
> > >
> >
> > It seems prepare function is doing some sanity checks before handing packets to
> > the HW.
> > So with this change all Tx paths calls the same Tx prepare function, if so why not
> > set the function pointer outside of the if block, instead of setting it in both legs
> > of the if/else? This clarifies that Tx prepare used always.
>
> Hi Ferruh,
>
> Yes, it make sense.
>
> Hi Konstantin,
Hi Leyi,
>
> Would that be something wrong if the prepare function goes for simple Tx function although it does not support the offload feature yet?
>
Current situation:
For simple TX path we set dev->tx_pkt_prepare = NULL.
That makes rte_eth_tx_prepare() a stub that does nothing and always returns: "All packets are good".
That is unsafe off-course, and if upper layer will pass a packet that is not supported,
then it can lead to various bad things: bad cksum, corrupted packets, TX hang, etc.
But at least it keeps simple TX path fast.
With that patch:
For simple TX path we set dev->tx_pkt_prepare = i40e_prep_pkts.
Now on TX path we invoke extra function that does a lot of checks, but it still unsafe:
as i40e_prep_pkts() assumes that full-featured TX function is in place (multi-segs are allowed, etc.).
So our simple TX path became slower, but still is unsafe.
I think that if we want to introduce tx_prepare() for simple TX path,
then the proper way - create a new function for it (i40e_simple_prep_pkts() or so).
It will be aware that simple TX path is in place and more restrictions should be met:
check that nb_segs==1 and no TX offloads (except FAST_FREE?) are enabled,
plus usual checks for min and max pkt_len.
Konstantin
next prev parent reply other threads:[~2021-04-08 10:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 8:53 Leyi Rong
2021-04-01 12:27 ` Zhang, Qi Z
2021-04-01 12:33 ` David Marchand
2021-04-01 13:19 ` Ananyev, Konstantin
2021-04-07 16:39 ` Ferruh Yigit
2021-04-08 8:29 ` Rong, Leyi
2021-04-08 10:32 ` Ananyev, Konstantin [this message]
2021-04-09 7:19 ` Rong, Leyi
2021-04-09 10:40 ` Ananyev, Konstantin
2021-04-13 10:23 ` Rong, Leyi
2021-04-13 10:41 ` Ananyev, Konstantin
2021-04-08 8:39 ` David Marchand
2021-04-08 8:49 ` Rong, Leyi
2021-04-19 8:36 ` [dpdk-dev] [PATCH v2] net/i40e: add Tx preparation for simple Tx " Leyi Rong
2021-04-19 9:36 ` Zhang, Qi Z
2021-04-19 10:59 ` Ananyev, Konstantin
2021-04-20 5:31 ` Rong, Leyi
2021-04-20 5:29 ` [dpdk-dev] [PATCH v3] " Leyi Rong
2021-04-20 8:03 ` Ananyev, Konstantin
2021-04-20 14:00 ` Zhang, Qi Z
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