![]() ![]() This option makes sense and is recommended only for the JVM with a couple of hundreds megabytes heap size, running in an environment with a single CPU. Independent of the number of cores available, just one is used by the JVM during garbage collection.Įnabling this collector for both the Young and Old Generation is done via specifying a single parameter in the JVM startup script: java -XX:+UseSerialGC ![]() This GC algorithm cannot thus take advantage of multiple CPU cores commonly found in modern hardware. Both collectors also trigger stop-the-world pauses, stopping all application threads. As the name implies – both of these collectors are single-threaded collectors, incapable of parallelizing the task at hand. This collection of garbage collectors uses mark-copy for the Young Generation and mark-sweep-compact for the Old Generation. G1, which encompasses collection of both Young and Old generations.Parallel New for Young + Concurrent Mark and Sweep (CMS) for the Old Generation.Parallel GC for both the Young and Old generations. #Jprofiler find garbage collector algorithm serialSerial GC for both the Young and Old generations.So, in the following chapters we cover the working principles of the following combinations: The rest are either deprecated, not supported or just impractical to apply in real world. ![]() In reality it all boils down to just four combinations highlighted in the table above. If the above looks too complex, do not worry. Note that this stands true for Java 8, for older Java versions the available combinations might differ a bit: Young In this chapter, the working principles of each of those algorithms will be explained.įor a quick cheat sheet, the following list is a fast way to get yourself up to speed with which algorithm combinations are possible. If you do not specify a garbage collection algorithm explicitly, a platform-specific default will be used. You can choose from a variety of such algorithms bundled into the JVM. An important aspect to recognize first is the fact that, for most JVMs out there, two different GC algorithms are needed – one to clean the Young Generation and another to clean the Old Generation. Now that we have reviewed the core concepts behind GC algorithms, let us move to the specific implementations one can find inside the JVM. ![]()
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