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Signed-Off-By: Pavel Šimerda <psimerda@redhat.com>
109 lines
3.3 KiB
Groff
109 lines
3.3 KiB
Groff
.TH FQ_CoDel 8 "4 June 2012" "iproute2" "Linux"
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.SH NAME
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CoDel \- Fair Queuing (FQ) with Controlled Delay (CoDel)
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.SH SYNOPSIS
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.B tc qdisc ... fq_codel
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[
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.B limit
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PACKETS ] [
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.B flows
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NUMBER ] [
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.B target
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TIME ] [
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.B interval
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TIME ] [
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.B quantum
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BYTES ] [
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.B ecn
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.B noecn
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]
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.SH DESCRIPTION
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FQ_Codel (Fair Queuing Controlled Delay) is queuing discipline that combines Fair
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Queuing with the CoDel AQM scheme. FQ_Codel uses a stochastic model to classify
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incoming packets into different flows and is used to provide a fair share of the
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bandwidth to all the flows using the queue. Each such flow is managed by the
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CoDel queuing discipline. Reordering within a flow is avoided since Codel
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internally uses a FIFO queue.
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.SH PARAMETERS
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.SS limit
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has the same semantics as
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.B codel
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and is the hard limit on the real queue size.
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When this limit is reached, incoming packets are dropped. Default is 10240
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packets.
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.SS flows
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is the number of flows into which the incoming packets are classified. Due to
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the stochastic nature of hashing, multiple flows may end up being hashed into
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the same slot. Newer flows have priority over older ones. This parameter can be
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set only at load time since memory has to be allocated for the hash table.
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Default value is 1024.
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.SS target
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has the same semantics as
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.B codel
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and is the acceptable minimum
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standing/persistent queue delay. This minimum delay is identified by tracking
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the local minimum queue delay that packets experience. Default value is 5ms.
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.SS interval
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has the same semantics as
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.B codel
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and is used to ensure that the measured minimum delay does not become too stale.
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The minimum delay must be experienced in the last epoch of length .B interval.
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It should be set on the order of the worst-case RTT through the bottleneck to
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give endpoints sufficient time to react. Default value is 100ms.
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.SS quantum
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is the number of bytes used as 'deficit' in the fair queuing algorithm. Default
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is set to 1514 bytes which corresponds to the Ethernet MTU plus the hardware
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header length of 14 bytes.
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.SS ecn | noecn
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has the same semantics as
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.B codel
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and can be used to mark packets instead of dropping them. If
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.B ecn
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has been enabled,
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.B noecn
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can be used to turn it off and vice-a-versa. Unlike
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.B codel, ecn
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is turned on by default.
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.SH EXAMPLES
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#tc qdisc add dev eth0 root fq_codel
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.br
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#tc -s qdisc show
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.br
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qdisc fq_codel 8002: dev eth0 root refcnt 2 limit 10240p flows 1024 quantum 1514
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target 5.0ms interval 100.0ms ecn
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Sent 428514 bytes 2269 pkt (dropped 0, overlimits 0 requeues 0)
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backlog 0b 0p requeues 0
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maxpacket 256 drop_overlimit 0 new_flow_count 0 ecn_mark 0
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new_flows_len 0 old_flows_len 0
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#tc qdisc add dev eth0 root fq_codel limit 2000 target 3ms interval 40ms noecn
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.br
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#tc -s qdisc show
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.br
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qdisc fq_codel 8003: dev eth0 root refcnt 2 limit 2000p flows 1024 quantum 1514
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target 3.0ms interval 40.0ms
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Sent 2588985006 bytes 1783629 pkt (dropped 0, overlimits 0 requeues 34869)
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backlog 0b 0p requeues 34869
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maxpacket 65226 drop_overlimit 0 new_flow_count 73 ecn_mark 0
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new_flows_len 1 old_flows_len 3
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.SH SEE ALSO
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.BR tc (8),
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.BR tc-codel (8),
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.BR tc-red (8)
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.SH AUTHORS
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FQ_CoDel was implemented by Eric Dumazet. This manpage was written
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by Vijay Subramanian. Please report corrections to the Linux Networking
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mailing list <netdev@vger.kernel.org>.
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