#88/add performance timing instrumentation

[yunlishao]

Summary

Adds opt-in performance timing instrumentation to TrafficLayer and VirEnvHelper to diagnose why FIXS co-simulation runs slower than real-time as traffic scales up.

This PR does not fix the performance issue - it adds measurement capabilities. Investigation found that SUMO's traffic_step degrades from ~3.5ms to ~20ms over ~2 minutes of simulation, which is a SUMO limitation.

Related Issues / Tasks

Closes #88

See investigation findings: #88 (comment)

Type of Change

• Bug fix
• New feature
• Maintenance / Refactor
• Documentation
• Test case / scenario update

Affected Modules / Components

• CommonLib/PerformanceTimer.h - new opt-in performance timing utility with PERF_LOG macro
• CommonLib/VirEnvHelper.cpp - socket timing at lines 423-428 (recv_socket), 405-452 (receive_realsim)
• TrafficLayer/TrafficLayer/mainTrafficLayer.cpp - timing at lines 911-1384 (main_loop), 917-943 (traffic_step)
• tests/UserScenarios/ - folder for proprietary user test cases

Code Snippets

recv_socket timing (VirEnvHelper.cpp:423-428)

PERF_TIC("recv_socket");
if (Sock_c.recvData(Sock_c.serverSock[iS], &simStateRecv, &simTimeRecv, Msg_c) < 0) {
    *errorMsg = "RealSim: Receive from traffic simulator failed";
    return ERROR_STEP_RECV_REALSIM;
}
PERF_TOC("recv_socket");

traffic_step timing (mainTrafficLayer.cpp:917-943)

PERF_TIC("traffic_step");
if (ENABLE_REALSIM && !g_shutdown.trafficSimulatorClosed) {
    try {
        Traffic_c.runOneStepSimulation();
    }
    catch (const std::exception& e) {
        // error handling...
    }
}
PERF_TOC("traffic_step");

Performance Logs

https://gist.github.com/yunlishao/f4d9dc8e9a0af653242db83ed909caaf

or download here:

• TrafficLayerPerf.log
• RealSimPerf.log

Test Cases

Performance logs generated from tests/UserScenarios/issue_88_runningSlowIssue/

Environment

• SUMO version: 1.21.0
• IPG CarMaker version: 13.1.2

Checklist

• Code compiles/runs as expected
• Tests pass locally
• Documentation is updated (if applicable)
• Relevant issues are linked
• Version-specific changes are noted (if any)

Additional Notes

Performance timing is opt-in via PERF_LOG macro to avoid overhead in normal builds.