Parallel Collector Changing NewRatio and SurvivorRatio

Java GC Tutorials - Herong's Tutorial Examples

∟Parallel Collector - "+XX:+UseParallelGC"

∟Parallel Collector Changing NewRatio and SurvivorRatio

This section demonstrates that the Parallel Collector changes the NewRatio and the SurvivorRatio dynamically, even they are specified in command line.

While testing the Parallel collector, I also noticed that it changes the NewRatio and the SurvivorRatio dynamically, even they are specified in command line. For example:

herong> java -Xms1200m -Xmx1200m -XX:NewRatio=1 -XX:SurvivorRatio=1 \
    -XX:+UseParallelGC -Xlog:gc=debug,gc+heap=debug GarbageCollection2

[debug][gc,heap] Minimum heap 1258291200  Initial heap 1258291200
                  Maximum heap 1258291200
[info ][gc     ] Using Parallel
Step/TotalMemory/FreeMemory/UsedMemory:
1   1048576000   1019201200   29374800
...
172   1048576000   839891968   208684032
[debug][gc,heap] GC(0) Heap before GC invocations=1 (full 0): PSYoungGen...
[debug][gc,heap] GC(0)   eden space 204800K, 99% used [...
[debug][gc,heap] GC(0)   to   space 204800K, 0% used [...
[debug][gc,heap] GC(0)  ParOldGen       total 614400K, used 0K [...
[debug][gc,heap] GC(0)   object space 614400K, 0% used [...

[info ][gc,heap] GC(0) PSYoungGen: 203793K->35808K(409600K)
[info ][gc,heap] GC(0) ParOldGen: 0K->8K(614400K)
[info ][gc     ] GC(0) Pause Young (Allocation Failure)
                       199M->34M(1000M) 11.262ms

[debug][gc,heap] GC(0) Heap after GC invocations=1 (full 0): PSYoungGen...
[debug][gc,heap] GC(0)   eden space 204800K, 0% used [...
[debug][gc,heap] GC(0)   from space 204800K, 17% used [...
[debug][gc,heap] GC(0)  ParOldGen       total 614400K, used 8K [...
[debug][gc,heap] GC(0)   object space 614400K, 0% used [...
   -- NewRatio almost respected as 1: 614400K/3*204800K
   -- SurvivorRatio respected perfectly as 1: 204800K/204800K

...
964   1048576000   802244880   246331120
[debug][gc,heap] GC(4) Heap before GC invocations=5 (full 0): PSYoungGen...
[debug][gc,heap] GC(4)   eden space 204800K, 99% used [...
[debug][gc,heap] GC(4)   from space 204800K, 17% used [...
[debug][gc,heap] GC(4)   to   space 204800K, 0% used [...
[debug][gc,heap] GC(4)  ParOldGen       total 614400K, used 32K [...
[debug][gc,heap] GC(4)   object space 614400K, 0% used [...

[info ][gc,heap] GC(4) PSYoungGen: 240525K->35760K(409600K)
[info ][gc,heap] GC(4) ParOldGen: 32K->40K(614400K)
[info ][gc     ] GC(4) Pause Young (Allocation Failure)
                       234M->34M(1000M) 7.335ms

[debug][gc,heap] GC(4) Heap after GC invocations=5 (full 0): PSYoungGen...
[debug][gc,heap] GC(4)   eden space 204800K, 0% used [...
[debug][gc,heap] GC(4)   from space 204800K, 17% used [...
[debug][gc,heap] GC(4)   to   space 35840K, 0% used [...
[debug][gc,heap] GC(4)   object space 614400K, 0% used [...

965   1048576000   1010867616   37708384
   -- "to" space size dynamically changed from 204800K to 35840K

1163   1048576000   802240432   246335568
[debug][gc,heap] GC(5) Heap before GC invocations=6 (full 0): PSYoungGen...
[debug][gc,heap] GC(5)   eden space 204800K, 99% used [...
[debug][gc,heap] GC(5)   from space 204800K, 17% used [...
[debug][gc,heap] GC(5)   to   space 35840K, 0% used [...
[debug][gc,heap] GC(5)   object space 614400K, 0% used [...

[info ][gc,heap] GC(5) PSYoungGen: 240522K->35808K(578560K)
[info ][gc,heap] GC(5) ParOldGen: 40K->48K(614400K)
[info ][gc     ] GC(5) Pause Young (Allocation Failure)
                       234M->35M(1165M) 9.329ms

[debug][gc,heap] GC(5) Heap after GC invocations=6 (full 0): PSYoungGen...
[debug][gc,heap] GC(5)   eden space 542720K, 0% used [...
[debug][gc,heap] GC(5)   from space 35840K, 99% used [...
[debug][gc,heap] GC(5)   to   space 35840K, 0% used [...
[debug][gc,heap] GC(5)   object space 614400K, 0% used [...
   -- NewRatio changed to: 614400K/578560K = 1.06
   -- SurvivorRatio changed to: 542720K/35840K = 15.14