This patch includes the man page of the PSPacer (Precise Software Pacing) qdisc module.
Signed-off-by: Ryousei Takano <[EMAIL PROTECTED]> --- man/man8/tc-psp.8 | 166 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 166 insertions(+), 0 deletions(-) create mode 100644 man/man8/tc-psp.8 diff --git a/man/man8/tc-psp.8 b/man/man8/tc-psp.8 new file mode 100644 index 0000000..a6e26bf --- /dev/null +++ b/man/man8/tc-psp.8 @@ -0,0 +1,166 @@ +.TH PSP 8 "13 October 2007" "iproute2" "Linux" +.SH NAME +PSP \- Precise Software Pacer +.SH SYNOPSIS +.B tc qdisc ... dev +dev +.B ( parent +classid +.B | root) [ handle +major: +.B ] psp [ default +minor-id +.B ] [ rate +rate +.B ] + +.B tc class ... dev +dev +.B parent +major:[minor] +.B [ classid +major:minor +.B ] psp rate +rate +.B ] [ mode +mode +.B ] + +.SH DESCRIPTION +Precise Software Pacer (PSPacer) is a classful queuing discipline +which controls traffic with +.BR tc (8) +command. +PSP achieves a precise pacing per class. + +.SH GAP PACKET +The key to realizing precise pacing is to control the starting time of +the transmission of each packet. We propose a simple yet accurate +mechanism to trigger the transmission of a packet. That is, to insert +a gap packet between the real packets. The gap packet produces a gap +between sequentially transmitted real packets. +We employ a PAUSE packet as a gap packet. A PAUSE packet is defined in +the IEEE 802.3x flow control. + +By changing the gap packet size, the starting time of +the next real packet transmission can be precisely controlled. +For example, to control a half rate transmission, a gap packet is inserted +between every real packet where the gap packet size is the same as +that of the real packets. + +.SH BYTE CLOCK SCHEDULING +Packet transmission is scheduled based on the inter-packet gap of each +class (i.e. target rate). +If the network has multiple bottleneck links, it is necessary to +schedule the order of packet transmission and the packet interval. + +PSPacer maintains a virtual clock which is counted by the total transmitted +byte instead of real time clock. Each sub-class has its local clock +which is used to make decision whether to send a packet or not. +If there is an idle time, a gap packet is inserted. + +.SH CLASSIFICATION +Within one PSP instance, many classes may exist. Each of these classes +contains its own qdisc. + +When enqueuing a packet, PSP starts at the root and uses various methods to +determine which class should be used to obtain the data to be enqueued. + +In the standard configuration, this process is rather easy. +At each node we look for an instruction, and then go to the class the +instruction refers to. If the class found is a leaf-node (without +children), we enqueue the packet there. If it is not yet a leaf node, we do +the same thing over again starting from that node. + +The following actions are performed in order at each node we visit, until +move to another node, or terminates the process. +.TP +(i) +Consult filters attached to the class. If we are at a leaf node, we are done. +Otherwise, restart. +.TP +(ii) +If none of the above returned with an instruction, send to the default class. +.P +./ This algorithm makes sure that a packet always ends up somewhere, even while +./ you are busy building your configuration. + +.SH QDISC +The root of a PSP qdisc class tree has the following parameters: + +.TP +parent major:minor | root +This mandatory parameter determines the place of the PSP instance, +either at the +.B root +of an interface or within an existing class. +.TP +handle major: +Like all other qdiscs, the PSP can be assigned a handle. It should consist only +of a major number, followed by a colon. Optional, but it is very useful +if classes will be generated within this qdisc. +.TP +default minor-id +Unclassified traffic is sent to the class with this minor-id. +.TP +rate rate +Optional. You can explicitly specify the maximum transmission rate. +For example, if a 33MHz/32bit PCI bus is used to connect a Gigabit +Ethernet network interface, the bottleneck is the PCI bus, and the +system can not transmit packets at the rate of gigabit/sec. + +.SH CLASSES +Classes have a host of parameters to configure their operation. + +.TP +parent major:minor +Specifies the place of this class within the hierarchy. If attached directly +to a qdisc and not to another class, minor can be omitted. Mandatory. +.TP +classid major:minor +Like qdiscs, classes can be named. The major number must be equal to the +major number of the qdisc to which it belongs. Optional, but needed if this +class is going to have children. +.TP +rate rate +Maximum transmission rate this class including all its children are assigned. +Optional, but required if this class is set to mode 1 (static target rate). +.TP +mode mode +Range from 0 to 1. The mode 0 is without pacing. The mode 1 is +pacing based on static target rate estimation. +Default is set to 0. + +.SH EXAMPLE +The output bandwidth of eth0 regulates at 500Mbps: +.in +5 + # tc qdisc add dev eth0 root handle 1: psp default 1 + # tc class add dev eth0 parent 1: classid 1:1 psp rate 500mbit + # tc qdisc add dev eth0 parent 1:1 handle 10: pfifo + +.SH TODO +.TP +o +In the current version, the dynamic target rate estimation mode is disabled. +.TP +o +TCP Segmentation Offloading (TSO) feature is not supported. +You must disable TSO by ethtool: +.in +5 +# /sbin/ethtool -K eth0 tso off + +.SH SOURCES +.TP +o +http://www.gridmpi.org/gridtcp.jsp +.TP +o +R.Takano, T.Kudoh, Y.Kodama, M.Matsuda, H.Tezuka, and Y.Ishikawa, +"Design and Evaluation of Precise Software Pacing Mechanisms for +Fast Long-Distance Networks," PFLDnet05, 2005. + +.SH SEE ALSO +.BR tc (8) + +.SH AUTHOR +Ryousei Takano <[EMAIL PROTECTED]>. -- 1.5.3.4 - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
