Minor GC and full GC

(1) Cenozoic (Eden + from Survior + to Survior) (proportional to 8:1:1, can be set by parameter –xx:survivorratio)

The JVM only uses Eden and one of its Survivor areas to serve objects at a time, and there is always a Survivor area that is idle.

The allocation was not guaranteed by the old age.

Old age: Arrays and large objects, which occur in the Cenozoic minor GC more than a certain number of times (default 15, can be set by-xx:maxtenuringthreshold) to move in objects

(2) Heap: Cenozoic + old age (approximately: 1:2, this value can be specified by parameter –xx:newratio)

Method Area: Permanent generation

Minor GC: occurs in the Cenozoic (replication algorithm) when the Eden Zone is full and survior does not cause a GC when full

Full GC: Refers to GC (marker cleanup algorithm) that occurred in the old age

(1) When the old age is full, the Gc,full GC will reclaim the young generation, the old generation

(2) The full GC will also be triggered when the permanent fill will cause the unload of class and method meta-information.

Minor GC, full GC trigger condition

Minor GC Trigger Condition: Minor GC is triggered when the Eden Zone is full.

Full GC Trigger conditions:

(1) when calling System.GC, the system recommends performing full GC, but does not necessarily execute

(2) Lack of space in the old age

(3) method to lack of space

(4) The average size of the old age after minor GC is greater than the available memory of the old age

(5) When the object size is larger than the available memory of the to space when it is copied from the Eden Zone and the From space area to the to space area, the object is dumped into the old age and the available memory in the old age is less than the object size

Frequently asked questions and solutions for full GC see this blog: Full GC