Update manual.

NEWS

@@ -25,6 +25,7 @@ v0.x.x (xxxx-xx-xx)
   can be now imported. A pseudo-TID will be created for each PID+TID pair
   in such circumstances.
 - Added support for custom source location tag ("loc") in chrome traces.
+- Sampling frequency can be now controlled using TRACY_SAMPLING_HZ macro.
 
 
 v0.7.7 (2021-04-01)

client/TracySysTrace.cpp

@@ -2,6 +2,33 @@
 
 #ifdef TRACY_HAS_SYSTEM_TRACING
 
+#ifndef TRACY_SAMPLING_HZ
+#  if defined _WIN32 || defined __CYGWIN__
+#    define TRACY_SAMPLING_HZ 8000
+#  elif defined __linux__
+#    define TRACY_SAMPLING_HZ 10000
+#  endif
+#endif
+
+namespace tracy
+{
+
+static constexpr int GetSamplingFrequency()
+{
+#if defined _WIN32 || defined __CYGWIN__
+    return TRACY_SAMPLING_HZ > 8000 ? 8000 : ( TRACY_SAMPLING_HZ < 1 ? 1 : TRACY_SAMPLING_HZ );
+#else
+    return TRACY_SAMPLING_HZ > 1000000 ? 1000000 : ( TRACY_SAMPLING_HZ < 1 ? 1 : TRACY_SAMPLING_HZ );
+#endif
+}
+
+static constexpr int GetSamplingPeriod()
+{
+    return 1000000000 / GetSamplingFrequency();
+}
+
+}
+
 #  if defined _WIN32 || defined __CYGWIN__
 
 #    ifndef NOMINMAX
@@ -330,6 +357,11 @@ static void SetupVsync()
 #endif
 }
 
+static constexpr int GetSamplingInterval()
+{
+    return GetSamplingPeriod() / 100;
+}
+
 bool SysTraceStart( int64_t& samplingPeriod )
 {
     if( !_GetThreadDescription ) _GetThreadDescription = (t_GetThreadDescription)GetProcAddress( GetModuleHandleA( "kernel32.dll" ), "GetThreadDescription" );
@@ -360,10 +392,10 @@ bool SysTraceStart( int64_t& samplingPeriod )
     if( isOs64Bit )
     {
         TRACE_PROFILE_INTERVAL interval = {};
-        interval.Interval = 1250;   // 8 kHz
+        interval.Interval = GetSamplingInterval();
         const auto intervalStatus = TraceSetInformation( 0, TraceSampledProfileIntervalInfo, &interval, sizeof( interval ) );
         if( intervalStatus != ERROR_SUCCESS ) return false;
-        samplingPeriod = 125*1000;
+        samplingPeriod = GetSamplingPeriod();
     }
 
     const auto psz = sizeof( EVENT_TRACE_PROPERTIES ) + sizeof( KERNEL_LOGGER_NAME );
@@ -649,7 +681,7 @@ static void SetupSampling( int64_t& samplingPeriod )
     return;
 #endif
 
-    samplingPeriod = 100*1000;
+    samplingPeriod = GetSamplingPeriod();
 
     s_numCpus = (int)std::thread::hardware_concurrency();
     s_ring = (RingBuffer<RingBufSize>*)tracy_malloc( sizeof( RingBuffer<RingBufSize> ) * s_numCpus );
@@ -660,7 +692,7 @@ static void SetupSampling( int64_t& samplingPeriod )
     pe.size = sizeof( perf_event_attr );
     pe.config = PERF_COUNT_SW_CPU_CLOCK;
 
-    pe.sample_freq = 10000;
+    pe.sample_freq = GetSamplingFrequency();
     pe.sample_type = PERF_SAMPLE_TID | PERF_SAMPLE_TIME | PERF_SAMPLE_CALLCHAIN;
 #if LINUX_VERSION_CODE >= KERNEL_VERSION( 4, 8, 0 )
     pe.sample_max_stack = 127;

manual/tracy.tex

@@ -1839,7 +1839,7 @@ Manual markup of zones doesn't cover every function existing in a program and ca
 
 This feature requires privilege elevation, as described in chapter~\ref{privilegeelevation}. Proper setup of the required program debugging data is described in chapter~\ref{collectingcallstacks}.
 
-On Windows sampling is performed at 8 kHz frequency (which is the maximum possible value), and on Linux and Android it is performed at 10 kHz.
+By default sampling is performed at 8 kHz frequency on Windows (which is the maximum possible value). On Linux and Android it is performed at 10 kHz. This value can be changed by providing the sampling frequency (in Hz) through the \texttt{TRACY\_SAMPLING\_HZ} macro.
 
 Call stack sampling may be disabled by using the \texttt{TRACY\_NO\_SAMPLING} define.