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giltene / jHiccup

jHiccup is a non-intrusive instrumentation tool that logs and records platform "hiccups" - including the JVM stalls that often happen when Java applications are executed and/or any OS or hardware platform noise that may cause the running application to not be continuously runnable.
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quick question about Interval_Max #27

Closed eostermueller closed 7 years ago

eostermueller commented 7 years ago

What is the unit or measure for Interval_Max in hiccup.*.hlog file ? "StartTimestamp","Interval_Length","Interval_Max","Interval_Compressed_Histogram"

Sure looks like milliseconds, but can't find it documented anywhere.

Thanks, --Erik

giltene commented 7 years ago

Yes, for jHiccup logs that is milliseconds (as a real number printed with 3 decimal points resolution). The log format is an HdrHistogram log. The encoded histogram is captured in nanosecond units, and the Interval_Max is reported (by default) in units that are 1,000,000.0 times that (which translates to milliseconds). The Interval_Max column is somewhat superfluous, as the value can be extracted from the encoded histogram itself. It is there for mainly human-readability (seeing just the timestamp and and the max is often useful when visually scanning text logs), and to make it easy for simple parsers that only need that information.

eostermueller commented 7 years ago

I consider myself a simple parser, so I'm glad to have it there. Thanks Gil.