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Message-ID: <SJ1PR11MB61804722400A816E3DB0AD51B8E19@SJ1PR11MB6180.namprd11.prod.outlook.com>
Date:   Thu, 15 Dec 2022 06:05:43 +0000
From:   "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
To:     "Gomes, Vinicius" <vinicius.gomes@...el.com>,
        "intel-wired-lan@...osl.org" <intel-wired-lan@...osl.org>
CC:     "tee.min.tan@...ux.intel.com" <tee.min.tan@...ux.intel.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "naamax.meir@...ux.intel.com" <naamax.meir@...ux.intel.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
Subject: RE: [PATCH net-next v1] igc: offload queue max SDU from tc-taprio

Hi Vinicius,

> -----Original Message-----
> From: Gomes, Vinicius <vinicius.gomes@...el.com>
> Sent: Thursday, 15 December, 2022 1:17 AM
> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>;
> intel-wired-lan@...osl.org
> Cc: tee.min.tan@...ux.intel.com; davem@...emloft.net; kuba@...nel.org;
> netdev@...r.kernel.org; Zulkifli, Muhammad Husaini
> <muhammad.husaini.zulkifli@...el.com>; naamax.meir@...ux.intel.com;
> Nguyen, Anthony L <anthony.l.nguyen@...el.com>
> Subject: Re: [PATCH net-next v1] igc: offload queue max SDU from tc-taprio
> 
> Hi,
> 
> Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com> writes:
> 
> > From: Tan Tee Min <tee.min.tan@...ux.intel.com>
> >
> > Add support for configuring the max SDU for each Tx queue.
> > If not specified, keep the default.
> >
> > Signed-off-by: Tan Tee Min <tee.min.tan@...ux.intel.com>
> > Signed-off-by: Muhammad Husaini Zulkifli
> > <muhammad.husaini.zulkifli@...el.com>
> > ---
> >  drivers/net/ethernet/intel/igc/igc.h      |  1 +
> >  drivers/net/ethernet/intel/igc/igc_main.c | 45
> +++++++++++++++++++++++
> >  include/net/pkt_sched.h                   |  1 +
> >  net/sched/sch_taprio.c                    |  4 +-
> >  4 files changed, 50 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/intel/igc/igc.h
> > b/drivers/net/ethernet/intel/igc/igc.h
> > index 5da8d162cd38..ce9e88687d8c 100644
> > --- a/drivers/net/ethernet/intel/igc/igc.h
> > +++ b/drivers/net/ethernet/intel/igc/igc.h
> > @@ -99,6 +99,7 @@ struct igc_ring {
> >
> >  	u32 start_time;
> >  	u32 end_time;
> > +	u32 max_sdu;
> >
> >  	/* CBS parameters */
> >  	bool cbs_enable;                /* indicates if CBS is enabled */
> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> > b/drivers/net/ethernet/intel/igc/igc_main.c
> > index e07287e05862..7ce05c31e371 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> > @@ -1508,6 +1508,7 @@ static netdev_tx_t igc_xmit_frame_ring(struct
> sk_buff *skb,
> >  	__le32 launch_time = 0;
> >  	u32 tx_flags = 0;
> >  	unsigned short f;
> > +	u32 max_sdu = 0;
> >  	ktime_t txtime;
> >  	u8 hdr_len = 0;
> >  	int tso = 0;
> > @@ -1527,6 +1528,16 @@ static netdev_tx_t igc_xmit_frame_ring(struct
> sk_buff *skb,
> >  		return NETDEV_TX_BUSY;
> >  	}
> >
> > +	if (tx_ring->max_sdu > 0) {
> > +		if (skb_vlan_tagged(skb))
> > +			max_sdu = tx_ring->max_sdu + VLAN_HLEN;
> > +		else
> > +			max_sdu = tx_ring->max_sdu;
> 
> perhaps this?
>     max_sdu = tx_ring->max_sdu + (skb_vlan_tagged(skb) ? VLAN_HLEN : 0);
> 
> Totally optional.

Sure. We can change to above suggestion.

> 
> > +
> > +		if (skb->len > max_sdu)
> > +			goto skb_drop;
> > +	}
> > +
> 
> I don't think the overhead would be measurable for the pkt/s rates that a
> 2.5G link can handle. But a test and a note in the commit message confirming
> that would be nice.

IMHO, it should not depends on the link speed but the packet size only.
If we detect packet size greater than max_sdu, we will just drop it.

> 
> >  	if (!tx_ring->launchtime_enable)
> >  		goto done;
> >
> > @@ -1606,6 +1617,12 @@ static netdev_tx_t igc_xmit_frame_ring(struct
> sk_buff *skb,
> >  	dev_kfree_skb_any(first->skb);
> >  	first->skb = NULL;
> >
> > +	return NETDEV_TX_OK;
> > +
> > +skb_drop:
> > +	dev_kfree_skb_any(skb);
> > +	skb = NULL;
> > +
> >  	return NETDEV_TX_OK;
> >  }
> >
> > @@ -6015,6 +6032,7 @@ static int igc_tsn_clear_schedule(struct
> > igc_adapter *adapter)
> >
> >  		ring->start_time = 0;
> >  		ring->end_time = NSEC_PER_SEC;
> > +		ring->max_sdu = 0;
> >  	}
> >
> >  	return 0;
> > @@ -6097,6 +6115,15 @@ static int igc_save_qbv_schedule(struct
> igc_adapter *adapter,
> >  		}
> >  	}
> >
> > +	for (i = 0; i < adapter->num_tx_queues; i++) {
> > +		struct igc_ring *ring = adapter->tx_ring[i];
> > +
> > +		if (qopt->max_frm_len[i] == U32_MAX)
> > +			ring->max_sdu = 0;
> > +		else
> > +			ring->max_sdu = qopt->max_frm_len[i];
> > +	}
> > +
> >  	return 0;
> >  }
> >
> > @@ -6184,12 +6211,30 @@ static int igc_tsn_enable_cbs(struct igc_adapter
> *adapter,
> >  	return igc_tsn_offload_apply(adapter);  }
> >
> > +static int igc_tsn_query_caps(struct tc_query_caps_base *base) {
> > +	switch (base->type) {
> > +	case TC_SETUP_QDISC_TAPRIO: {
> > +		struct tc_taprio_caps *caps = base->caps;
> > +
> > +		caps->supports_queue_max_sdu = true;
> > +
> > +		return 0;
> > +	}
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> > +}
> > +
> >  static int igc_setup_tc(struct net_device *dev, enum tc_setup_type type,
> >  			void *type_data)
> >  {
> >  	struct igc_adapter *adapter = netdev_priv(dev);
> >
> >  	switch (type) {
> > +	case TC_QUERY_CAPS:
> > +		return igc_tsn_query_caps(type_data);
> > +
> >  	case TC_SETUP_QDISC_TAPRIO:
> >  		return igc_tsn_enable_qbv_scheduling(adapter, type_data);
> >
> > diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index
> > 38207873eda6..d2539b1f6529 100644
> > --- a/include/net/pkt_sched.h
> > +++ b/include/net/pkt_sched.h
> > @@ -178,6 +178,7 @@ struct tc_taprio_qopt_offload {
> >  	u64 cycle_time;
> >  	u64 cycle_time_extension;
> >  	u32 max_sdu[TC_MAX_QUEUE];
> > +	u32 max_frm_len[TC_MAX_QUEUE];
> >
> 
> 'max_frm_len' is an internal taprio optimization, to simplify the code where
> the underlying HW doesn't support offload.

The max_sdu only comes with MTU payload size. The reason why we are using 
this max_frm_len is to get the header + MTU size together. 

We can use max_sdu + header in the igc_save_qbv_schedule() and remove 
this piece of code from pkt_sched.h

> 
> For offloading, only 'max_sdu' should be used. Unless you have a strong
> reason. If you have that reason, it should be a separate commit.
> 
> >  	size_t num_entries;
> >  	struct tc_taprio_sched_entry entries[]; diff --git
> > a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index
> > 570389f6cdd7..d39164074756 100644
> > --- a/net/sched/sch_taprio.c
> > +++ b/net/sched/sch_taprio.c
> > @@ -1263,8 +1263,10 @@ static int taprio_enable_offload(struct
> net_device *dev,
> >  	offload->enable = 1;
> >  	taprio_sched_to_offload(dev, sched, offload);
> >
> > -	for (tc = 0; tc < TC_MAX_QUEUE; tc++)
> > +	for (tc = 0; tc < TC_MAX_QUEUE; tc++) {
> >  		offload->max_sdu[tc] = q->max_sdu[tc];
> > +		offload->max_frm_len[tc] = q->max_frm_len[tc];
> > +	}
> >
> >  	err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, offload);
> >  	if (err < 0) {
> > --
> > 2.17.1
> >
> 
> --
> Vinicius

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