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diff --git a/man/man8/tc-fq_pie.8 b/man/man8/tc-fq_pie.8 new file mode 100644 index 0000000..457a56b --- /dev/null +++ b/man/man8/tc-fq_pie.8 @@ -0,0 +1,166 @@ +.TH FQ-PIE 8 "23 January 2020" "iproute2" "Linux" + +.SH NAME + +FQ-PIE - Flow Queue Proportional Integral controller Enhanced + +.SH SYNOPSIS + +.B tc qdisc ... fq_pie +[ \fBlimit\fR PACKETS ] [ \fBflows\fR NUMBER ] +.br + \ +[ \fBtarget\fR TIME ] [ \fBtupdate\fR TIME ] +.br + \ +[ \fBalpha\fR NUMBER ] [ \fBbeta\fR NUMBER ] +.br + \ +[ \fBquantum\fR BYTES ] [ \fBmemory_limit\fR BYTES ] +.br + \ +[ \fBecn_prob\fR PERENTAGE ] [ [\fBno\fR]\fBecn\fR ] +.br + \ +[ [\fBno\fR]\fBbytemode\fR ] [ [\fBno_\fR]\fBdq_rate_estimator\fR ] + +.SH DESCRIPTION +FQ-PIE (Flow Queuing with Proportional Integral controller Enhanced) is a +queuing discipline that combines Flow Queuing with the PIE AQM scheme. FQ-PIE +uses a Jenkins hash function to classify incoming packets into different flows +and is used to provide a fair share of the bandwidth to all the flows using the +qdisc. Each such flow is managed by the PIE algorithm. + +.SH ALGORITHM +The FQ-PIE algorithm consists of two logical parts: the scheduler which selects +which queue to dequeue a packet from, and the PIE AQM which works on each of the +queues. The major work of FQ-PIE is mostly in the scheduling part. The +interaction between the scheduler and the PIE algorithm is straight forward. + +During the enqueue stage, a hashing-based scheme is used, where flows are hashed +into a number of buckets with each bucket having its own queue. The number of +buckets is configurable, and presently defaults to 1024 in the implementation. +The flow hashing is performed on the 5-tuple of source and destination IP +addresses, port numbers and IP protocol number. Once the packet has been +successfully classified into a queue, it is handed over to the PIE algorithm +for enqueuing. It is then added to the tail of the selected queue, and the +queue's byte count is updated by the packet size. If the queue is not currently +active (i.e., if it is not in either the list of new or the list of old queues) +, it is added to the end of the list of new queues, and its number of credits +is initiated to the configured quantum. Otherwise, the queue is left in its +current queue list. + +During the dequeue stage, the scheduler first looks at the list of new queues; +for the queue at the head of that list, if that queue has a negative number of +credits (i.e., it has already dequeued at least a quantum of bytes), it is given +an additional quantum of credits, the queue is put onto the end of the list of +old queues, and the routine selects the next queue and starts again. Otherwise, +that queue is selected for dequeue again. If the list of new queues is empty, +the scheduler proceeds down the list of old queues in the same fashion +(checking the credits, and either selecting the queue for dequeuing, or adding +credits and putting the queue back at the end of the list). After having +selected a queue from which to dequeue a packet, the PIE algorithm is invoked +on that queue. + +Finally, if the PIE algorithm does not return a packet, then the queue must be +empty and the scheduler does one of two things: + +If the queue selected for dequeue came from the list of new queues, it is moved +to the end of the list of old queues. If instead it came from the list of old +queues, that queue is removed from the list, to be added back (as a new queue) +the next time a packet arrives that hashes to that queue. Then (since no packet +was available for dequeue), the whole dequeue process is restarted from the +beginning. + +If, instead, the scheduler did get a packet back from the PIE algorithm, it +subtracts the size of the packet from the byte credits for the selected queue +and returns the packet as the result of the dequeue operation. + +.SH PARAMETERS +.SS limit +It is the limit on the queue size in packets. Incoming packets are dropped when +the limit is reached. The default value is 10240 packets. + +.SS flows +It is the number of flows into which the incoming packets are classified. Due +to the stochastic nature of hashing, multiple flows may end up being hashed +into the same slot. Newer flows have priority over older ones. This +parameter can be set only at load time since memory has to be allocated for +the hash table. The default value is 1024. + +.SS target +It is the queue delay which the PIE algorithm tries to maintain. The default +target delay is 15ms. + +.SS tupdate +It is the time interval 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 quantum +quantum signifies the number of bytes that may be dequeued from a queue before +switching to the next queue in the deficit round robin scheme. + +.SS memory_limit +It is the maximum total memory allowed for packets of all flows. The default is +32Mb. + +.SS ecn_prob +It is the drop probability threshold below which packets will be ECN marked +instead of getting dropped. The default is 10%. Setting this parameter requires +\fBecn\fR to be enabled. + +.SS \fR[\fBno\fR]\fBecn\fR +It has the same semantics as \fBpie\fR and can be used to mark packets +instead of dropping them. If \fBecn\fR has been enabled, \fBnoecn\fR can +be used to turn it off and vice-a-versa. + +.SS \fR[\fBno\fR]\fBbytemode\fR +It is used to scale drop probability proportional to packet size +\fBbytemode\fR to turn on bytemode, \fBnobytemode\fR to turn off +bytemode. By default, \fBbytemode\fR is turned off. + +.SS \fR[\fBno_\fR]\fBdq_rate_estimator\fR +\fBdq_rate_estimator\fR can be used to calculate queue delay using Little's +Law, \fBno_dq_rate_estimator\fR can be used to calculate queue delay +using timestamp. By default, \fBdq_rate_estimator\fR is turned off. + +.SH EXAMPLES +# tc qdisc add dev eth0 root fq_pie +.br +# tc -s qdisc show dev eth0 +.br +qdisc fq_pie 8001: root refcnt 2 limit 10240p flows 1024 target 15.0ms tupdate +16.0ms alpha 2 beta 20 quantum 1514b memory_limit 32Mb ecn_prob 10 + Sent 159173586 bytes 105261 pkt (dropped 24, overlimits 0 requeues 0) + backlog 75700b 50p requeues 0 + pkts_in 105311 overlimit 0 overmemory 0 dropped 24 ecn_mark 0 + new_flow_count 7332 new_flows_len 0 old_flows_len 4 memory_used 108800 + +# tc qdisc add dev eth0 root fq_pie dq_rate_estimator +.br +# tc -s qdisc show dev eth0 +.br +qdisc fq_pie 8001: root refcnt 2 limit 10240p flows 1024 target 15.0ms tupdate +16.0ms alpha 2 beta 20 quantum 1514b memory_limit 32Mb ecn_prob 10 +dq_rate_estimator + Sent 8263620 bytes 5550 pkt (dropped 4, overlimits 0 requeues 0) + backlog 805448b 532p requeues 0 + pkts_in 6082 overlimit 0 overmemory 0 dropped 4 ecn_mark 0 + new_flow_count 94 new_flows_len 0 old_flows_len 8 memory_used 1157632 + +.SH SEE ALSO +.BR tc (8), +.BR tc-pie (8), +.BR tc-fq_codel (8) + +.SH SOURCES +RFC 8033: https://tools.ietf.org/html/rfc8033 + +.SH AUTHORS +FQ-PIE was implemented by Mohit P. Tahiliani. Please report corrections to the +Linux Networking mailing list <netdev@vger.kernel.org>. |