Count missed samples when estimating total CPU time in ctimer mode#1068
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Count missed samples when estimating total CPU time in ctimer mode#1068
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apangin
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Description
Leverage
si_overrunfor scaling total CPU time counted inctimermode.Motivation and context
Sampling frequency in ctimer mode depends on the kernel
CONFIG_HZconfiguration, which is typically 250 or 100 Hz. This means, profiling intervals should be multiple of 4ms/10ms, or they will not work as expected.Fortunately, if profiling interval is set to a smaller value, Linux will pass the number of missed samples (number of times the timer would have triggered) in
si_overrunfield ofsiginfo. We can use this value to compute actual CPU time.How has this been tested?
Usual tests + new
ctimerTotalanditimerTotalunit tests.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.