Messages in this thread | | | Date | Mon, 28 Dec 2009 12:16:33 +0100 | From | Tim Blechmann <> | Subject | perf: counter and event question |
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hi all,
trying to use the perf subsystem, i am a bit confused by the terms `performance counter' and `performance event'.
i am trying to compare `counting' counters with `sampling' counters. as a test case, i am counting PERF_COUNT_HW_INSTRUCTIONS of the same code piece with both approaches. the sampling counters are sampled with a period of 1. the code is really trivial [1].
the `counting' counters report numbers of about 9000 instructions, but the mmap buffer only seems to contain about 100 to 200 event samples. from my (limited) understanding, these number should at least be similar, so i am a bit confused to see such a big difference. am i missing something, like it is impossible to sample instructions with a period of 1? or could there be an issue with my code?
thanks, tim
[1] http://tim.klingt.org/git?p=perf-cpp.git
-- tim@klingt.org http://tim.klingt.org
I don't write music for sissy ears. Charles Ives
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