NAME
FQ - Fair Queue traffic policingSYNOPSIS
tc qdisc ... fq [ limit PACKETS ] [ flow_limit PACKETS ] [ quantum BYTES ] [ initial_quantum BYTES ] [ maxrate RATE ] [ buckets NUMBER ] [ orphan_mask NUMBER ] [ pacing | nopacing ] [ ce_threshold TIME ]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 hash is used as fallback.PARAMETERS
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.flow_limit
Hard limit on the maximum number of packets queued per flow. Default value is 100.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.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.maxrate
Maximum sending rate of a flow. Default is unlimited. Application specific setting via SO_MAX_PACING_RATE is ignored only if it is larger than this value.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.orphan_mask
For packets not owned by a socket, fq is able to mask a part of skb->hash and reduce number of buckets associated with the traffic. This is a DDOS prevention mechanism, and the default is 1023 (meaning no more than 1024 flows are allocated for these packets)[no]pacing
Enable or disable flow pacing. Default is enabled.ce_threshold
sets a threshold above which all packets are marked with ECN Congestion Experienced. This is useful for DCTCP-style congestion control algorithms that require marking at very shallow queueing thresholds.EXAMPLES
#tc qdisc add dev eth0 root fq ce_threshold 4msSent 72149092 bytes 48062 pkt (dropped 2176, overlimits 0 requeues 0)
backlog 1937920b 1280p requeues 0
flows 34 (inactive 17 throttled 0)
gc 0 highprio 0 throttled 0 ce_mark 47622 flows_plimit 2176
SEE ALSO
tc(8), socket(7)AUTHORS
FQ was written by Eric Dumazet.10 Sept 2015 | iproute2 |