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diff --git a/man/man8/tc-pie.8 b/man/man8/tc-pie.8 new file mode 100644 index 0000000..5a8c782 --- /dev/null +++ b/man/man8/tc-pie.8 @@ -0,0 +1,148 @@ +.TH PIE 8 "16 January 2014" "iproute2" "Linux" +.SH NAME +PIE \- Proportional Integral controller-Enhanced AQM algorithm +.SH SYNOPSIS +.B tc qdisc ... pie +[ +.B limit +PACKETS ] [ +.B target +TIME ] [ +.B tupdate +TIME ] [ +.B alpha +int ] [ +.B beta +int ] [ +.B ecn +| +.B noecn +] [ +.B bytemode +| +.B nobytemode +] [ +.B dq_rate_estimator +| +.B no_dq_rate_estimator +] + +.SH DESCRIPTION +Proportional Integral controller-Enhanced (PIE) is a control theoretic active +queue management scheme. It is based on the proportional integral controller but +aims to control delay. The main design goals are + o Low latency control + o High link utilization + o Simple implementation + o Guaranteed stability and fast responsiveness + +.SH ALGORITHM +PIE is designed to control delay effectively. First, an average dequeue rate is +estimated based on the standing queue. The rate is used to calculate the current +delay. Then, on a periodic basis, the delay is used to calculate the dropping +probability. Finally, on arrival, a packet is dropped (or marked) based on this +probability. + +PIE makes adjustments to the probability based on the trend of the delay i.e. +whether it is going up or down.The delay converges quickly to the target value +specified. + +alpha and beta are statically chosen parameters chosen to control the drop probability +growth and are determined through control theoretic approaches. alpha determines how +the deviation between the current and target latency changes probability. beta exerts +additional adjustments depending on the latency trend. + +The drop probability is used to mark packets in ecn mode. However, as in RED, +beyond 10% packets are dropped based on this probability. The bytemode is used +to drop packets proportional to the packet size. + +Additional details can be found in the paper cited below. + +.SH PARAMETERS +.SS limit +limit on the queue size in packets. Incoming packets are dropped when this limit +is reached. Default is 1000 packets. + +.SS target +is the expected queue delay. The default target delay is 15ms. + +.SS tupdate +is the frequency at which the system drop probability is calculated. The default is 15ms. + +.SS alpha +.SS beta +alpha and beta are parameters chosen to control the drop probability. These +should be in the range between 0 and 32. + +.SS ecn | noecn +is used to mark packets instead of dropping. +.B ecn +to turn on ecn mode, +.B noecn +to turn off ecn mode. By default, +.B ecn +is turned off. + +.SS bytemode | nobytemode +is used to scale drop probability proportional to packet size. +.B bytemode +to turn on bytemode, +.B nobytemode +to turn off bytemode. By default, +.B bytemode +is turned off. + +.SS dq_rate_estimator | no_dq_rate_estimator +is used to calculate delay using Little's law. +.B dq_rate_estimator +to turn on dq_rate_estimator, +.B no_dq_rate_estimator +to turn off no_dq_rate_estimator. By default, +.B dq_rate_estimator +is turned off. + +.SH EXAMPLES + # tc qdisc add dev eth0 root pie + # tc -s qdisc show + qdisc pie 8036: dev eth0 root refcnt 2 limit 1000p target 15.0ms tupdate 16.0ms alpha 2 beta 20 + Sent 31216108 bytes 20800 pkt (dropped 80, overlimits 0 requeues 0) + backlog 16654b 11p requeues 0 + prob 0.006161 delay 15666us + pkts_in 20811 overlimit 0 dropped 80 maxq 50 ecn_mark 0 + + # tc qdisc add dev eth0 root pie dq_rate_estimator + # tc -s qdisc show + qdisc pie 8036: dev eth0 root refcnt 2 limit 1000p target 15.0ms tupdate 16.0ms alpha 2 beta 20 + Sent 63947420 bytes 42414 pkt (dropped 41, overlimits 0 requeues 0) + backlog 271006b 179p requeues 0 + prob 0.000092 delay 22200us avg_dq_rate 12145996 + pkts_in 41 overlimit 343 dropped 0 maxq 50 ecn_mark 0 + + # tc qdisc add dev eth0 root pie limit 100 target 20ms tupdate 30ms ecn + # tc -s qdisc show + qdisc pie 8036: dev eth0 root refcnt 2 limit 100p target 20.0ms tupdate 32.0ms alpha 2 beta 20 ecn + Sent 6591724 bytes 4442 pkt (dropped 27, overlimits 0 requeues 0) + backlog 18168b 12p requeues 0 + prob 0.008845 delay 11348us + pkts_in 4454 overlimit 0 dropped 27 maxq 65 ecn_mark 0 + + # tc qdisc add dev eth0 root pie limit 100 target 50ms tupdate 30ms bytemode + # tc -s qdisc show + qdisc pie 8036: dev eth0 root refcnt 2 limit 100p target 50.0ms tupdate 32.0ms alpha 2 beta 20 bytemode + Sent 1616274 bytes 1137 pkt (dropped 0, overlimits 0 requeues 0) + backlog 13626b 9p requeues 0 + prob 0.000000 delay 0us + pkts_in 1146 overlimit 0 dropped 0 maxq 23 ecn_mark 0 + +.SH SEE ALSO +.BR tc (8), +.BR tc-codel (8) +.BR tc-red (8) + +.SH SOURCES + o RFC 8033: https://tools.ietf.org/html/rfc8033 + +.SH AUTHORS +PIE was implemented by Vijay Subramanian and Mythili Prabhu, also the authors of +this man page. Please report bugs and corrections to the Linux networking +development mailing list at <netdev@vger.kernel.org>. |