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List:       oprofile-list
Subject:    Re: How to relate execution time to the CYCLE sampling?
From:       Robert Richter <robert.richter () amd ! com>
Date:       2009-08-21 8:31:12
Message-ID: 20090821083112.GB9915 () erda ! amd ! com
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On 21.08.09 14:13:50, Paul Yuan wrote:
> I increase the sampling interval to 100,001 and find the result is
> reasonable to estimate the execution time. But the sampling result is not
> reliable if the interval is below 100,001.
> 
> I also evaluate the intervals of 300,001 and 500,001 for CPU_CLK_UNHALTED,
> and the sampling result scales well.

You might lose samples with short intervals. Check:

 cat /dev/oprofile/stats/cpu*/sample_lost_overflow

Increase the buffer-size with the opcontrol --cpu-buffer-size and
--buffer-size options.

Also, the oprofile load for sampling increases with short intervals.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@amd.com


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