Adding upstream version 6.1.0.upstream/6.1.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 166 insertions, 0 deletions

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+.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>.