8. Performance > Performance Monitoring
191
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
8.2.3
Bottleneck Detection
Monitoring the queue depth of the inbound and outbound modules can detect bottleneck traffic in the
RapidIO interfaces. It can also be used to determine the period of time that packets of a given priority
and below cannot be accepted. Both the inbound and outbound directions have the ability to program a
queue depth watermark. The number of times that the queue depth watermark is exceeded is counted.
As well, the amount of time that the queue depth watermark is exceeded is also counted to a
programmable degree of accuracy. A port-write and/or an interrupt can be asserted if the queue depth
watermark value exceeds a programmable number.
The registers in the outbound direction that contain the values and counters described above are:
•
“RapidIO Port x Transmitter Output Queue Depth Threshold Register” on page 350
•
“RapidIO Port x Transmitter Output Queue Congestion Status Register” on page 352
•
“RapidIO Port x Transmitter Output Queue Congestion Period Register” on page 354
The registers in the inbound direction are:
•
“RapidIO Port x Receiver Input Queue Depth Threshold Register” on page 355
•
“RapidIO Port x Receiver Input Queue Congestion Status Register” on page 357
•
“RapidIO Port x Receiver Input Queue Congestion Period Register” on page 359
8.2.4
Congestion Detection
A packet is reordered when it cannot make forward progress through the internal switching fabric.
Packet reordering can be a sign of congestion in a RapidIO interface. A count of the number of times
packets are reordered in each interface is stored in the
“RapidIO Port x Reordering Counter Register”
. After the value in a programmable threshold is reached, an interrupt is triggered.
For example, if the traffic is time-critical control data, a very low threshold is programmed so that it is
not congested for long. The interrupt handler is invoked. The system host can then take action to help
ease the congestion.
8.2.5
Resetting Performance Registers
The Inbound and Outbound performance registers are both read and writable. These registers are
cleared after every read and saturate at the maximum counter values.