Why does PAPI_overflow, PAPI_profil and PAPI_sprofil work strangely with a small threshold?
On most systems, overflow must be emulated in software by PAPI. Only on the UltraSparc III, Itanium and IRIX does the operating system support true interrupt on overflow. Therefore the user is advised on most platforms to make sure the overflow value is no more than 1/1000th the clock rate. The emulation handler in PAPI runs every millisecond, therefore the goal of the tool designer should be to pick an value that will overflow frequently but not too frequently. Not following these guidelines could result in either the overflows never occurring or overflows occurring on every interrupt and thus resulting in a flat profile.
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- Why does PAPI_overflow, PAPI_profil and PAPI_sprofil work strangely with a small threshold?
