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linux/net/sched
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Eric Dumazet a5d2809040 codel: fix maxpacket/mtu confusion 
Under presence of TSO/GSO/GRO packets, codel at low rates can be quite
useless. In following example, not a single packet was ever dropped,
while average delay in codel queue is ~100 ms !

qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms
 Sent 134376498 bytes 88797 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 13626b 3p requeues 0
  count 0 lastcount 0 ldelay 96.9ms drop_next 0us
  maxpacket 9084 ecn_mark 0 drop_overlimit 0

This comes from a confusion of what should be the minimal backlog. It is
pretty clear it is not 64KB or whatever max GSO packet ever reached the
qdisc.

codel intent was to use MTU of the device.

After the fix, we finally drop some packets, and rtt/cwnd of my single
TCP flow are meeting our expectations.

qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms
 Sent 102798497 bytes 67912 pkt (dropped 1365, overlimits 0 requeues 0)
 backlog 6056b 3p requeues 0
  count 1 lastcount 1 ldelay 36.3ms drop_next 0us
  maxpacket 10598 ecn_mark 0 drop_overlimit 0

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kathleen Nichols <nichols@pollere.com>
Cc: Dave Taht <dave.taht@gmail.com>
Cc: Van Jacobson <vanj@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-03 22:17:40 -04:00
..
act_api.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
act_bpf.c bpf: fix bpf helpers to use skb->mac_header relative offsets 2015-04-16 14:08:49 -04:00
act_connmark.c net: sched: act_connmark: don't zap skb->nfct 2015-04-29 14:56:40 -04:00
act_csum.c net: sched: fix skb->protocol use in case of accelerated vlan path 2015-01-13 17:51:08 -05:00
act_gact.c sched: fix act file names in header comment 2014-11-06 15:04:41 -05:00
act_ipt.c sched: fix act file names in header comment 2014-11-06 15:04:41 -05:00
act_mirred.c act_mirred: Fix bogus header when redirecting from VLAN 2015-04-17 13:29:28 -04:00
act_nat.c net_sched: act: move tcf_hashinfo_init() into tcf_register_action() 2014-02-12 19:23:32 -05:00
act_pedit.c sched: fix act file names in header comment 2014-11-06 15:04:41 -05:00
act_police.c sched: fix act file names in header comment 2014-11-06 15:04:41 -05:00
act_simple.c sched: fix act file names in header comment 2014-11-06 15:04:41 -05:00
act_skbedit.c net_sched: act: move tcf_hashinfo_init() into tcf_register_action() 2014-02-12 19:23:32 -05:00
act_vlan.c sched: introduce vlan action 2014-11-21 14:20:18 -05:00
cls_api.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_basic.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_bpf.c bpf: fix bpf helpers to use skb->mac_header relative offsets 2015-04-16 14:08:49 -04:00
cls_cgroup.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_flow.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_fw.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_route.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_rsvp.c
cls_rsvp.h net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_rsvp6.c
cls_tcindex.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
cls_u32.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-03-20 18:51:09 -04:00
em_canid.c net: sched: remove tcf_proto from ematch calls 2014-10-06 18:02:32 -04:00
em_cmp.c
em_ipset.c net: sched: fix skb->protocol use in case of accelerated vlan path 2015-01-13 17:51:08 -05:00
em_meta.c net: rename vlan_tx_* helpers since "tx" is misleading there 2015-01-13 17:51:08 -05:00
em_nbyte.c net: sched: remove tcf_proto from ematch calls 2014-10-06 18:02:32 -04:00
em_text.c net: Remove state argument from skb_find_text() 2015-02-22 15:59:54 -05:00
em_u32.c
ematch.c ematch: Fix auto-loading of ematch modules. 2015-02-20 15:30:56 -05:00
Kconfig Merge branch 'kconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2015-02-19 10:36:45 -08:00
Makefile net: sched: Introduce connmark action 2015-01-19 16:02:06 -05:00
sch_api.c net_sched: destroy proto tp when all filters are gone 2015-03-09 15:35:55 -04:00
sch_atm.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_blackhole.c
sch_cbq.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_choke.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_codel.c codel: fix maxpacket/mtu confusion 2015-05-03 22:17:40 -04:00
sch_drr.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_dsmark.c net: sched: fix skb->protocol use in case of accelerated vlan path 2015-01-13 17:51:08 -05:00
sch_fifo.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_fq.c pkt_sched: fq: correct spelling of locally 2015-04-01 22:52:29 -04:00
sch_fq_codel.c codel: fix maxpacket/mtu confusion 2015-05-03 22:17:40 -04:00
sch_generic.c net_sched: restore qdisc quota fairness limits after bulk dequeue 2014-10-09 19:12:26 -04:00
sch_gred.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_hfsc.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_hhf.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_htb.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_ingress.c net: use jump label patching for ingress qdisc in __netif_receive_skb_core 2015-04-13 13:34:40 -04:00
sch_mq.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_mqprio.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_multiq.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_netem.c netem: Fixes byte backlog accounting for the first of two chained netem instances 2015-04-07 18:34:24 -04:00
sch_pie.c sch_pie: schedule the timer after all init succeed 2014-10-29 14:28:01 -04:00
sch_plug.c
sch_prio.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_qfq.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_red.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_sfb.c net: sched: implement qstat helper routines 2014-09-30 01:02:26 -04:00
sch_sfq.c net: sched: enable per cpu qstats 2014-09-30 01:02:26 -04:00
sch_tbf.c net: sched: avoid costly atomic operation in fq_dequeue() 2014-10-06 00:55:10 -04:00
sch_teql.c net: sched: fix skb->protocol use in case of accelerated vlan path 2015-01-13 17:51:08 -05:00