IPCLatency Sample

Source files for measuring the latency for switching between two threads.

Source Files

File	Description
IPCLatency.c	The main source file.

Building the Sample

Build the sample in any of the four available configurations: Debug, Release (to build IPCLatency.exe) or RTSSDebug, RTSSRelease (to build IPCLatency.rtss).

Running the Sample

Start the Subsystem through wRTOS Settings or wRTOS Control Panel, and then run this command:

RTSSrun IPCLatency.rtss [options]

Options

Option	Description	Default
-t <num>	Trip method: 1 = Event 2 = Mutex 3 = Semaphore 4 = Yield 5 = Priority 6 = No Trip 7 = Release Semaphore	1
-i <num>	Outer loop count (test rounds)	1000
-j <num>	Inner loop count (iterations per round)	10000
-d <num>	Delay between outer loops (ms)	30
-m <num>	Pentium speed estimate (for ns conversion)	200

Expected Results

• A PASS or FAIL status
• PASS: Threads alternate correctly and complete all iterations.
• FAIL: Thread counters were out of sync.
• A minimum, maximum, and average latency (in ns)
• The number of samples
• A histogram of latencies
• (If under RTSS) A timing breakdown with and without timer interrupt

Remarks

• Use different -t values to test various thread-switch mechanisms.
• For baseline measurement, use -t 6 (No Trip) or -t 7 (Release Semaphore).
• Histogram resolution is controlled by the RESOLUTION and NBUCKETS macros.