Garbage Collectors - JRockit

TL;DR

• Dynamic (default one)

• Throughput – for maximum throughput (default):  –XgcPrio:throughput

• Pausetime – for short and even pause times: –XgcPrio:pausetime

• Deterministic – for very short and deterministic pause times (requires Oracle JRockit Real Time)

• Static (1x Generational, 2x Concurrent, 1x Parallel)

• Generational

• Generational Copy: -Xgc:gencopy

• Concurrent

• Single-spaced mostly concurrent: –Xgc:singlecon

• Generational mostly concurrent: –Xgc:gencon

• Parallel

• General parallel: –Xgc:genpar

Details:

Static:

• Generational Copy:
• best to use with small heap and for testing purposes
• splits heap into generations

• Generational parallel collector:

• causes longer pauses/ stop-the-world
• multiple threads to speed up the process
• segments the heap into nursery and tenured generations (objects that survive two cycles are promoted from nursery to tenured generation)
• use when the application has many short lived objects
• Concurrent:

• Single-spaced mostly concurrent collector:
• almost no pauses
• works concurrently
• uses entire heap
• will not pause the application as long as it can collect dead objects
• Generational mostly concurrent collector:
• frequent stop-the-world
• splits the heap -> parallel on nursery, concurrent on tenured generation
• shorter nursery will cause more objects in tenured, hence more stop-the-world
• Parallel:
• Single-spaced parallel collector:

• causes longer pauses/ stop-the-world
• multiple threads to speed up the process
• does not segment heap into multiple generations
• use when the application has more long lived objects

Dynamic:

Throughput:

"The higher the memory throughput the shorter is the time between the two events. Moreover, the higher the memory throughput the smaller the heap you will need."

 PauseTime:

" The longer the pause, the more unresponsive your system will be. The worst pause time and the average pause time are the two most interesting values you can use for tuning the system."