JDK-7178361 : G1: Make sure that PrintGC and PrintGCDetails use the same timing for the GC pause
- Type: Bug
- Component: hotspot
- Sub-Component: gc
- Affected Version: hs24
- Priority: P3
- Status: Resolved
- Resolution: Fixed
- OS: generic
- CPU: generic
- Submitted: 2012-06-20
- Updated: 2013-09-18
- Resolved: 2012-07-24
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| JDK 7 | JDK 8 | Other |
|---|---|---|
7u40Fixed  |
8Fixed |
hs24Fixed |
Description
-XX:+PrintGC and -XX:+PrintGCDetails use different timers to track the G1 collection pauses. It turns out that the timing used by -XX:+PrintGCDetails only covers part of the pause. Running SPECjbb2005 I got GC pause logging like this: PrintGCDetails: 13 ms PrtinGC: 57 ms PrintSafepointStatistics: 61 ms The PrintSafepointStatistics is as close to the actual pause as we can get. PrintGC does not cover the whole pause but is fairly close. PrintGCDetails is missing a large part of the pause. To analyze G1 performance we normally run with PrintGCDetails, so it is important that this information is correct.
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