http://java.sun.com/performance/reference/whitepapers/tuning.html
CMSのデフォルト設定: SurvivorRatio=1024 MaxTenuringThreshold=0
→ Scavenge GCの全ての survivors を昇格させる
→ デフォルト設定は survivors を積極的に昇格させCMSコレクタで回収させる？
4.2.6 Tuning Example 6: Tuning for low pause times and high throughput
This tuning example similar to Example 2, but uses the concurrent garbage collector (instead of the parallel throughput collector).
java -Xmx3550m -Xms3550m -Xmn2g -Xss128k -XX:ParallelGCThreads=20 -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:MaxTenuringThreshold=31
Comments:
-XX:+UseConcMarkSweepGC -XX:+UseParNewGC
Selects the Concurrent Mark Sweep collector. This collector may deliver better response time properties for the application (i.e., low application pause time). It is a parallel and mostly-concurrent collector and and can be a good match for the threading ability of an large multi-processor systems.
-XX:SurvivorRatio=8
Sets survivor space ratio to 1:8, resulting in larger survivor spaces (the smaller the ratio, the larger the space). Larger survivor spaces allow short lived objects a longer time period to die in the young generation.
-XX:TargetSurvivorRatio=90
Allows 90% of the survivor spaces to be occupied instead of the default 50%, allowing better utilization of the survivor space memory.
-XX:MaxTenuringThreshold=31
Allows short lived objects a longer time period to die in the young generation (and hence, avoid promotion). A consequence of this setting is that minor GC times can increase due to additional objects to copy. This value and survivor space sizes may need to be adjusted so as to balance overheads of copying between survivor spaces versus tenuring objects that are going to live for a long time. The default settings for CMS are SurvivorRatio=1024 and MaxTenuringThreshold=0 which cause all survivors of a scavenge to be promoted. This can place a lot of pressure on the single concurrent thread collecting the tenured generation. Note: when used with -XX:+UseBiasedLocking, this setting should be 15.
