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Date: Thu, 15 Dec 2022 13:04:40 -0300
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...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 Husaini,
"Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
writes:
> 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.
>
I was thinking more about the added conditional on the hot path, if it
had some performance impact for the case when packets are not dropped. I
really don't think there will be any, but it's nice to have some numbers
to confirm that.
>>
>> > 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
This sounds better, only exposing max_sdu to the drivers, even if it
causes a bit of duplicated code.
>
>>
>> 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
--
Vinicius
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