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Kurt Kanzenbach 497cc00224 taprio: Handle short intervals and large packets 
When using short intervals e.g. below one millisecond, large packets won't be
transmitted at all. The software implementations checks whether the packet can
be fit into the remaining interval. Therefore, it takes the packet length and
the transmission speed into account. That is correct.

However, for large packets it may be that the transmission time exceeds the
interval resulting in no packet transmission. The same situation works fine with
hardware offloading applied.

The problem has been observed with the following schedule and iperf3:

|tc qdisc replace dev lan1 parent root handle 100 taprio \
|   num_tc 8 \
|   map 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 \
|   queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \
|   base-time $base \
|   sched-entry S 0x40 500000 \
|   sched-entry S 0xbf 500000 \
|   clockid CLOCK_TAI \
|   flags 0x00

[...]

|root@tsn:~# iperf3 -c 192.168.2.105
|Connecting to host 192.168.2.105, port 5201
|[  5] local 192.168.2.121 port 52610 connected to 192.168.2.105 port 5201
|[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
|[  5]   0.00-1.00   sec  45.2 KBytes   370 Kbits/sec    0   1.41 KBytes
|[  5]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec    0   1.41 KBytes

After debugging, it seems that the packet length stored in the SKB is about
7000-8000 bytes. Using a 100 Mbit/s link the transmission time is about 600us
which larger than the interval of 500us.

Therefore, segment the SKB into smaller chunks if the packet is too big. This
yields similar results than the hardware offload:

|root@tsn:~# iperf3 -c 192.168.2.105
|Connecting to host 192.168.2.105, port 5201
|- - - - - - - - - - - - - - - - - - - - - - - - -
|[ ID] Interval           Transfer     Bitrate         Retr
|[  5]   0.00-10.00  sec  48.9 MBytes  41.0 Mbits/sec    0             sender
|[  5]   0.00-10.02  sec  48.7 MBytes  40.7 Mbits/sec                  receiver

Furthermore, the segmentation can be skipped for the full offload case, as the
driver or the hardware is expected to handle this.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2021-03-19 11:32:44 -07:00
..
Kconfig net: sched: incorrect Kconfig dependencies on Netfilter modules 2020-12-09 15:49:29 -08:00
Makefile net/sched: sch_frag: add generic packet fragment support. 2020-11-27 14:36:02 -08:00
act_api.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-02-16 17:51:13 -08:00
act_bpf.c net: sched: fix misspellings using misspell-fixer tool 2020-11-10 17:00:28 -08:00
act_connmark.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_csum.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_ct.c net: flow_offload: Add original direction flag to ct_metadata 2021-01-29 18:05:30 -08:00
act_ctinfo.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-05 18:40:01 -07:00
act_gact.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_gate.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-05 18:40:01 -07:00
act_ife.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_ipt.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
act_meta_mark.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_meta_skbprio.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_meta_skbtcindex.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_mirred.c net/sched: sch_frag: add generic packet fragment support. 2020-11-27 14:36:02 -08:00
act_mpls.c net/sched: act_mpls: ensure LSE is pullable before reading it 2020-12-03 11:13:37 -08:00
act_nat.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_pedit.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_police.c net/sched: act_police: add support for packet-per-second policing 2021-03-13 14:18:09 -08:00
act_sample.c psample: Encapsulate packet metadata in a struct 2021-03-14 15:00:43 -07:00
act_simple.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
act_skbedit.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_skbmod.c net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
act_tunnel_key.c net/sched: act_tunnel_key: fix OOB write in case of IPv6 ERSPAN tunnels 2020-10-20 21:10:41 -07:00
act_vlan.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-05 18:40:01 -07:00
cls_api.c flow_offload: add support for packet-per-second policing 2021-03-13 14:18:09 -08:00
cls_basic.c net_sched: fix ops->bind_class() implementations 2020-01-27 10:51:43 +01:00
cls_bpf.c net_sched: fix ops->bind_class() implementations 2020-01-27 10:51:43 +01:00
cls_cgroup.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cls_flow.c Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
cls_flower.c net/sched: cls_flower: validate ct_state for invalid and reply flags 2021-02-23 12:23:44 -08:00
cls_fw.c net_sched: fix ops->bind_class() implementations 2020-01-27 10:51:43 +01:00
cls_matchall.c net: qos offload add flow status with dropped count 2020-06-19 12:53:30 -07:00
cls_route.c net_sched: cls_route: remove the right filter from hashtable 2020-03-16 01:59:32 -07:00
cls_rsvp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cls_rsvp.h net: sched: fix misspellings using misspell-fixer tool 2020-11-10 17:00:28 -08:00
cls_rsvp6.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cls_tcindex.c net_sched: avoid shift-out-of-bounds in tcindex_set_parms() 2021-01-15 18:11:10 -08:00
cls_u32.c net/sched: cls_u32: simplify the return expression of u32_reoffload_knode() 2020-12-08 16:22:53 -08:00
em_canid.c net: sched: kerneldoc fixes 2020-07-13 17:20:40 -07:00
em_cmp.c net: sched: fix misspellings using misspell-fixer tool 2020-11-10 17:00:28 -08:00
em_ipset.c sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
em_ipt.c sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
em_meta.c sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
em_nbyte.c net: sched: Return the correct errno code 2021-02-06 11:15:28 -08:00
em_text.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
em_u32.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
ematch.c net: sched: kerneldoc fixes 2020-07-13 17:20:40 -07:00
sch_api.c net: sched: avoid duplicates in classes dump 2021-03-04 14:27:47 -08:00
sch_atm.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_blackhole.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_cake.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
sch_cbq.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_cbs.c net: don't include ethtool.h from netdevice.h 2020-11-23 17:27:04 -08:00
sch_choke.c net: sched: prevent invalid Scell_log shift count 2020-12-28 14:52:54 -08:00
sch_codel.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_drr.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_dsmark.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_etf.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_ets.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_fifo.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_fq.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_fq_codel.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-08-05 20:13:21 -07:00
sch_fq_pie.c net/sched: fq_pie: initialize timer earlier in fq_pie_init() 2020-12-04 14:15:01 -08:00
sch_frag.c net/sched: sch_frag: add generic packet fragment support. 2020-11-27 14:36:02 -08:00
sch_generic.c net/sched: act_police: add support for packet-per-second policing 2021-03-13 14:18:09 -08:00
sch_gred.c net: sched: prevent invalid Scell_log shift count 2020-12-28 14:52:54 -08:00
sch_hfsc.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_hhf.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_htb.c sch_htb: Stats for offloaded HTB 2021-01-22 20:41:29 -08:00
sch_ingress.c net: sched: Pass ingress block to tcf_classify_ingress 2020-02-19 17:49:48 -08:00
sch_mq.c net: sched: fix dump qlen for sch_mq/sch_mqprio with NOLOCK subqueues 2019-12-03 11:53:55 -08:00
sch_mqprio.c mqprio: Fix out-of-bounds access in mqprio_dump 2019-12-06 11:58:45 -08:00
sch_multiq.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_netem.c netem: fix zero division in tabledist 2020-10-29 11:45:47 -07:00
sch_pie.c net: sched: fix misspellings using misspell-fixer tool 2020-11-10 17:00:28 -08:00
sch_plug.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_prio.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_qfq.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_red.c net: sched: prevent invalid Scell_log shift count 2020-12-28 14:52:54 -08:00
sch_sfb.c net: sched: Add extack to Qdisc_class_ops.delete 2021-01-22 20:41:29 -08:00
sch_sfq.c net: sched: prevent invalid Scell_log shift count 2020-12-28 14:52:54 -08:00
sch_skbprio.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_taprio.c taprio: Handle short intervals and large packets 2021-03-19 11:32:44 -07:00
sch_tbf.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_teql.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00