It's paused a second time at the end of the CMS GC phase, to account for the objects that were missed during the concurrent cycle, when application threads updated the objects after CMS GC were completed. It's paused first when it marks a live object that's directly reachable. In the case of CMS GC, the application is paused twice. If you're still using a Java version that has it, though, you can enable it with: $ java -XX:+UseConcMarkSweepGC This GC was deprecated in Java 8u, and completely removed from 14u onwards. This is suitable for applications with low pause time. This GC runs concurrently with the application, which slows the response time of the application. Compaction for live objects isn't performed in CMS GC after deleting the unused objects, so the time paused is less than in other methods. It uses multiple threads for both minor and major GC. Concurrent Mark Sweep (CMS)Ĭoncurrent Mark Sweep (CMS) garbage collection is run alongside an application. There's also a version of Parallel GC called Parallel Old GC, which uses multiple threads for both young and old generations: $ java -XX:+UseParallelOldGC 3. With this option, minor GC in the young generation is done with multiple threads, but GC and compaction is done with a single thread in the old generation. Parallel GC can be explicitly enabled: java -XX:+UseParallelGC.Throughput (time spent for GC compared to actual application execution): -XX:GCTimeRatio=.Number of threads: -XX:ParallelGCThreads=.Various GC parameters, like throughput, pause time, number of threads, and footprint, can be tuned with suitable JVM flags: This is the default GC in JVM, and is also known as the Throughput Collector. This type of GC is suitable for applications with medium to large data sets running in a multithreaded and multiprocessor environment. But in this case, there are multiple threads performing GC operation. That means that while GC is happening, application threads are paused.
#Learn java reddit serial#
Like Serial GC, this also uses a "stop the world" method.