GitHub user bheuvel opened a pull request:
https://github.com/apache/cloudstack/pull/1324
Factor in inaccurancy of System.nanoTime in class Profiler
The time diff measurement by the class Profiler, is done by
System.nanoTime().
System.nanoTime() is not 100% accurate (lots of info on this on the web).
The inaccurance seems to vary/depend with different dependencies
(multi-core/OS/kernels).
Problem:
In my case the code which measures `Thread.sleep(ONE_SECOND);` ~~takes~~
measures 999 milliseconds, which breaks the test expecting the sleep of 1000
milliseconds to ~~take~~ measure at least 1000 milliseconds.
Solution:
A `MARGIN` (of 100 milliseconds) is already present to factor in some time
for overhead/surrounding code which adds time. Another margin could be added to
factor in the possible time measurement error.
To limit additional lines of code, the constant `ONE_SECOND`, which is used
by the testcase (sleep), is increased from 1000 milliseconds to `1000l +
(MARGIN / 10)` (effectively 1010 milliseconds).
Thereby the inaccurancy on my system of ~1% ("faster") is caught as the
`sleep(1010)` is measured as '1009' milliseconds.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/bheuvel/cloudstack testprofiler-second
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/cloudstack/pull/1324.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1324
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commit dbb10a4ed5dc763b4c603e5cc3f2b70a202c0a2b
Author: Bob <bvandenheu...@schubergphilis.com>
Date: 2016-01-08T12:31:27Z
Factor in inaccurancy of System.nanoTime
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