JDK-8148359 : Improve concurrent mark thread synchronization on startup
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P4
  • Status: Closed
  • Resolution: Duplicate
  • Submitted: 2016-01-27
  • Updated: 2019-11-22
  • Resolved: 2019-11-22
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tbdResolved
Related Reports
Duplicate :  
JDK-8221392 - Reduce ConcurrentGCThreads spinning during start up
Relates :  
JDK-8172792 - JEP 308: Improve Dynamic Number of Thread Sizing for G1
Relates :  
JDK-8136854 - G1 ConcurrentG1RefineThread::stop delays JVM shutdown for >150ms
Description
In JDK-8136854 we found that the current code to synchronize the concurrent mark thread with the main thread during initialization uses a polling loop with a (previously) large delay.

In very short running applications (microbenchmarks) this caused very slow startup of G1. In JDK-8136854 this problem has been resolved by decreasing this delay significantly.

However it would likely be much better to use a notify/wait scheme for this to avoid any kind of polling loop, which seems a much "nicer" solution.

This CR is to prototype this and evaluate it against the current solution.