JAVA: JAVA MEMORY MANAGEMENT

JAVA MEMORY MANAGEMENT

Low Latency - One fast answer

High Throughput – All answers as fast as possible

JVM – Write once, run anywhere

Minor GC – moves the live objects from Eden space to Survivor spaces. If the objects are old enough then they are promoted to Old Generation space.

TenuringThreshold -Number of times the object has been copied between Survivor spaces. Default 7

Avoid large object allocations – which may directly go in Old Gen pace

The Objects will be placed in Finalizer queue and the queue will not necessary run everytime a GC cycle runs.

CMS – is good and runs currently along with application threads

No Compaction of data– we have to use free list and has fragmentation of heap

When Minor GC runs, it will free-up the space in Eden and Survivor1 and copies the live copies to Survivor2.

It stores as logically continuous area then physically

When Minor GC, happens

After Minor GC completion

The Eden space and survivor is empty now, the remaining live objects are copied to other survivor space region and the live objects which are promoted are copied to Old Gen region.

JVM parameters in Java - JVM option it can be divided into two parts:

1) JVM Options that begin with -X are non-standard (thy are not guaranteed to be supported on all JVM implementations), and are subject to change without notice in subsequent releases of the JDK.

2) JVM Options or parameters which are specified with -XX are not stable and are not recommended for casual use. These options are subject to change without notice also.