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Date: Mon, 21 Sep 2015 19:24:50 +0200 From: Florian Westphal <fw@...len.de> To: <netdev@...r.kernel.org> Cc: Florian Westphal <fw@...len.de>, Phil Sutter <phil@....cc> Subject: [PATCH iproute] man: tc: add man page for fq pacer Partially based on kernel Kconfig help text, code comments and git commit messages from Eric Dumazet. Joint work with Phil Sutter. Signed-off-by: Phil Sutter <phil@....cc> Signed-off-by: Florian Westphal <fw@...len.de> --- Note, this doesn't document 'refill_delay' option proposed in https://patchwork.ozlabs.org/patch/516301/ . Eric seemed to prefer to not mention this option. man/man8/Makefile | 1 + man/man8/tc-fq.8 | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ man/man8/tc.8 | 1 + 3 files changed, 94 insertions(+) create mode 100644 man/man8/tc-fq.8 diff --git a/man/man8/Makefile b/man/man8/Makefile index 3df9961..d0e1b1e 100644 --- a/man/man8/Makefile +++ b/man/man8/Makefile @@ -2,6 +2,7 @@ TARGETS = ip-address.8 ip-link.8 ip-route.8 MAN8PAGES = $(TARGETS) ip.8 arpd.8 lnstat.8 routel.8 rtacct.8 rtmon.8 ss.8 \ tc.8 tc-bfifo.8 tc-bpf.8 tc-cbq.8 tc-cbq-details.8 tc-choke.8 tc-codel.8 \ + tc-fq.8 \ tc-drr.8 tc-ematch.8 tc-fq_codel.8 tc-hfsc.8 tc-htb.8 tc-pie.8 \ tc-mqprio.8 tc-netem.8 tc-pfifo.8 tc-pfifo_fast.8 tc-prio.8 tc-red.8 \ tc-sfb.8 tc-sfq.8 tc-stab.8 tc-tbf.8 \ diff --git a/man/man8/tc-fq.8 b/man/man8/tc-fq.8 new file mode 100644 index 0000000..993beb6 --- /dev/null +++ b/man/man8/tc-fq.8 @@ -0,0 +1,92 @@ +.TH FQ 8 "10 Sept 2015" "iproute2" "Linux" +.SH NAME +Fair Queuing (FQ) \- Traffic Pacing +.SH SYNOPSIS +.B tc qdisc ... fq +[ +.B limit +PACKETS ] [ +.B flow_limit +PACKETS ] [ +.B quantum +BYTES ] [ +.B initial_quantum +BYTES ] [ +.B maxrate +RATE ] [ +.B buckets +NUMBER ] [ +.B pacing +| +.B nopacing +] + +.SH DESCRIPTION +FQ (Fair Queue) is a classless packet scheduler meant to be mostly +used for locally generated traffic. It is designed to achieve per flow pacing. +FQ does flow separation, and is able to respect pacing requirements set by TCP stack. +All packets belonging to a socket are considered as a 'flow'. +For non local packets (router workload), packet rxhash is used as fallback. + +An application can specify a maximum pacing rate using the +.B SO_MAX_PACING_RATE +setsockopt call. This packet scheduler adds delay between packets to +respect rate limitation set by TCP stack. + +Dequeueing happens in a round-robin fashion. +A special FIFO queue is reserved for high priority packets ( +.B TC_PRIO_CONTROL +priority), such packets are always dequeued first. + +FQ is non-work-conserving. + +TCP pacing is good for flows having idle times, as the congestion +window permits TCP stack to queue a possibly large number of packets. +This removes the 'slow start after idle' choice, badly hitting +large BDP flows and applications delivering chunks of data such as video streams. + +.SH PARAMETERS +.SS limit +Hard limit on the real queue size. When this limit is reached, new packets +are dropped. If the value is lowered, packets are dropped so that the new limit is +met. Default is 10000 packets. +.SS flow_limit +Hard limit on the maximum number of packets queued per flow. +Default value is 100. +.SS quantum +The credit per dequeue RR round, i.e. the amount of bytes a flow is allowed to +dequeue at once. A larger value means a longer time period before the next flow +will be served. +Default is 2 * interface MTU bytes. +.SS initial_quantum +The initial sending rate credit, i.e. the amount of bytes a new flow is allowed +to dequeue initially. +This is specifically meant to allow using IW10 without added delay. +Default is 10 * interface MTU, i.e. 15140 for 'standard' ethernet. +.SS maxrate +Maximum sending rate of a flow. Default is unlimited. +Application specific setting via +.B SO_MAX_PACING_RATE +is ignored only if it is larger than this value. +.SS buckets +The size of the hash table used for flow lookups. Each bucket is assigned a +red-black tree for efficient collision sorting. +Default: 1024. +.SS [no]pacing +Enable or disable flow pacing. Default is enabled. +.SH EXAMPLES +#tc qdisc add dev eth0 root fq +.br +#tc -s -d qdisc +.br +qdisc fq 8003: dev eth0 root refcnt 2 limit 10000p flow_limit 100p buckets 1024 quantum 3028 initial_quantum 15140 + Sent 503727981 bytes 1146972 pkt (dropped 0, overlimits 0 requeues 54452) + backlog 0b 0p requeues 54452 + 1289 flows (1289 inactive, 0 throttled) + 0 gc, 31 highprio, 27411 throttled +.br +.SH SEE ALSO +.BR tc (8), +.BR socket (7) +.SH AUTHORS +FQ was written by Eric Dumazet. diff --git a/man/man8/tc.8 b/man/man8/tc.8 index feafa05..d35e053 100644 --- a/man/man8/tc.8 +++ b/man/man8/tc.8 @@ -564,6 +564,7 @@ was written by Alexey N. Kuznetsov and added in Linux 2.2. .BR tc-codel (8), .BR tc-drr (8), .BR tc-ematch (8), +.BR tc-fq (8), .BR tc-fq_codel (8), .BR tc-hfsc (7), .BR tc-hfsc (8), -- 2.0.5 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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