Fix #1337 : On Linux respect max sample rate#1342
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wolfpld merged 4 commits intowolfpld:masterfrom Apr 20, 2026
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This forces to (re)use frequency values as input, which may be changed by the platform code later on. This way we have a single "source of truth" for sample freq. Also removed the Win32 `GetSamplingInterval` which was a wrapper above `GetSamplingPeriod` but its value would be divided again anyway.
…void lost events This may be especially useful for low performance machines. We also warn about this behaviour through TracyDebug which ends up in Messages.
wolfpld
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Apr 20, 2026
wolfpld
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Apr 20, 2026
| int microseconds = GetSamplingInterval() / 10; | ||
| samplingPeriod = SamplingFrequencyToPeriodNs( GetSamplingFrequency() ); | ||
| const int microseconds = samplingPeriod / 1000; | ||
| if( etw::EnableCPUProfiling( session_kernel, microseconds ) != ERROR_SUCCESS ) |
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Yeah it was also using GetSamplingPeriod() that I replaced, and GetSamplingInterval was adding an indirection for nothing (dividing by 100, then divided by 10 at call site).
Alternative (not touching GetSamplingInterval) would have been to introduce yet another function or write the 1000000000 / samplingHz inline in the linux code.
Your call
wolfpld
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Apr 20, 2026
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On Linux, Tracy was ignoring the system's maximum perf sampling rate, which could cause dropped events — particularly on low-performance or embedded systems.
This PR reads
/proc/sys/kernel/perf_event_max_sample_rateat startup and caps the requested frequency to the system maximum if needed. A debug message is emitted when the rate is reduced.The refactor of
GetSamplingPeriod→SamplingFrequencyToPeriodNsis included to ensure the reportedsamplingPeriodalways reflects the actual (possibly capped) frequency used.Note:
/proc/sys/kernel/perf_event_max_sample_rate's value is non-zero since torvalds/linux@723478c but I could had a null-check if needed.