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Port Throttling


Revision as of 12:42, 25 October 2011 by (talk) (Current Throttled Ports)
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Sometimes the frame rate from Output Ports has to be rate limited. The ThrottledOutputPortDecorator allows rate limits to be configured on OutputPorts using a Token Bucket Algorithm.

The following example shows applying the ThrottledOutputPortDecorator to an Output port to rate limit the output.

Before (no throttling):

OutputPort *output_port = new UsbProOutputPort(this, 0, "");

After (throttle to 190 frames per second)

OutputPort *output_port = new ThrottledOutputPortDecorator(
      new UsbProOutputPort(this, 0, ""),  // the port to throttle
      plugin_adaptor->WakeUpTime(),  // the select server wake up time
      10,  // start with 10 tokens in the bucket                                                                                                                  
      190);  // throttle to 190 frames per second

When port throttling is in place, messages will appear at log level 4 similar to:

PortDecorators.h:48: Port rated limited, dropping frame

Current Throttled Ports

For some devices, values can be changed in ~/.ola/ola-usbserial.conf