UPR statement

UPR statement = "UPR", {UPR attribute};

UPR attribute = "MAX",     "=", constant |

                "BUFFERS", "=", constant;

The UPR statement allows you to tune various settings in the Universal Packet Router (UPR) system task.

MAX attribute

The MAX attribute specifies the maximum size of UPR network packets, in octets. The virtual channel mechanism transmits messages across the processor network in packets that can be any size from 4 octets up to MAX octets; messages larger than MAX are split into a number of smaller messages. The default setting for MAX is 3072 octets. Increasing this value will speed up UPR communications if fewer UPR packets are then required to transmit a message of a given size. On the other hand, decreasing MAX reduces the amount of memory required for UPR packet buffers.

MAX must be an exact multiple of 128 and less than 65532.

BUFFERS attribute

UPR runs a number of virtual links over each physical link under its control. The number of virtual links on each physical link is calculated by the configurer and depends only on the network topology: it is not directly related to the number of virtual connections routed over that link. For each virtual link, UPR allocates a number of buffers; the default is two. Increasing the number of buffers on a virtual link may increase the performance of communications over that virtual link, particularly for long messages routed through intermediate nodes.

The BUFFERS attribute of the UPR statement can be used to change the number of buffers that are allocated to each virtual link. The new setting applies to all processors, except where the BUFFERS attribute of an individual PROCESSOR statement is used to override it. The number of buffers specified must be in the range 1 to 50, inclusive. The size of each buffer is controlled by the MAX attribute of the UPR statement; see above.