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* $Id: pa_cpuload.c 1097 2006-08-26 08:27:53Z rossb $
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* Portable Audio I/O Library CPU Load measurement functions
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* Portable CPU load measurement facility.
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* Based on the Open Source API proposed by Ross Bencina
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* Copyright (c) 2002 Ross Bencina
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files
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* (the "Software"), to deal in the Software without restriction,
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* including without limitation the rights to use, copy, modify, merge,
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* publish, distribute, sublicense, and/or sell copies of the Software,
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* and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
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* ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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* The text above constitutes the entire PortAudio license; however,
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* the PortAudio community also makes the following non-binding requests:
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* Any person wishing to distribute modifications to the Software is
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* requested to send the modifications to the original developer so that
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* they can be incorporated into the canonical version. It is also
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* requested that these non-binding requests be included along with the
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@brief Functions to assist in measuring the CPU utilization of a callback
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stream. Used to implement the Pa_GetStreamCpuLoad() function.
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@todo Dynamically calculate the coefficients used to smooth the CPU Load
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Measurements over time to provide a uniform characterisation of CPU Load
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independent of rate at which PaUtil_BeginCpuLoadMeasurement /
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PaUtil_EndCpuLoadMeasurement are called.
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#include "pa_cpuload.h"
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#include "pa_util.h" /* for PaUtil_GetTime() */
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void PaUtil_InitializeCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer, double sampleRate )
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assert( sampleRate > 0 );
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measurer->samplingPeriod = 1. / sampleRate;
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measurer->averageLoad = 0.;
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void PaUtil_ResetCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer )
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measurer->averageLoad = 0.;
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void PaUtil_BeginCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer )
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measurer->measurementStartTime = PaUtil_GetTime();
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void PaUtil_EndCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer, unsigned long framesProcessed )
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double measurementEndTime, secondsFor100Percent, measuredLoad;
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if( framesProcessed > 0 ){
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measurementEndTime = PaUtil_GetTime();
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assert( framesProcessed > 0 );
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secondsFor100Percent = framesProcessed * measurer->samplingPeriod;
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measuredLoad = (measurementEndTime - measurer->measurementStartTime) / secondsFor100Percent;
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/* Low pass filter the calculated CPU load to reduce jitter using a simple IIR low pass filter. */
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/** FIXME @todo these coefficients shouldn't be hardwired */
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#define LOWPASS_COEFFICIENT_0 (0.9)
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#define LOWPASS_COEFFICIENT_1 (0.99999 - LOWPASS_COEFFICIENT_0)
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measurer->averageLoad = (LOWPASS_COEFFICIENT_0 * measurer->averageLoad) +
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(LOWPASS_COEFFICIENT_1 * measuredLoad);
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double PaUtil_GetCpuLoad( PaUtilCpuLoadMeasurer* measurer )
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return measurer->averageLoad;