java - Minor GC 太慢

Question

java version "1.6.0_17"
Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)


-server -Xmx3000m -Xms3000m -Xmn650m -XX:PermSize=256M -XX:MaxPermSize=256m 
-XX:+DisableExplicitGC -XX:+UseParNewGC -XX:ParallelGCThreads=8 
-XX:+PrintTenuringDistribution -XX:+UseConcMarkSweepGC 
-XX:+UseCMSCompactAtFullCollection -XX:+CMSParallelRemarkEnabled -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseParNewGC 

58876.976: [GC 58876.976: [ParNew
Desired survivor size 34078720 bytes, new threshold 1 (max 4)
- age   1:   35092080 bytes,   35092080 total
: 599040K->55380K(599040K), 0.3054020 secs] 1594716K->1113571K(3005440K), 0.3058680 secs] [Times: user=1.85 sys=0.05, real=0.31 secs]
59109.884: [GC 59109.884: [ParNew
Desired survivor size 34078720 bytes, new threshold 4 (max 4)
- age   1:   30958856 bytes,   30958856 total
: 587860K->39545K(599040K), 0.1958710 secs] 1646051K->1131839K(3005440K), 0.1963230 secs] [Times: user=1.26 sys=0.01, real=0.19 secs]
59399.831: [GC 59399.831: [ParNew
Desired survivor size 34078720 bytes, new threshold 1 (max 4)
- age   1:   36009176 bytes,   36009176 total
- age   2:   29223424 bytes,   65232600 total
: 572025K->66560K(599040K), 0.1467870 secs] 1664319K->1162057K(3005440K), 0.1472820 secs] [Times: user=1.11 sys=0.02, real=0.15 secs]
59721.070: [GC 59721.071: [ParNew
Desired survivor size 34078720 bytes, new threshold 1 (max 4)
- age   1:   42097920 bytes,   42097920 total
: 599040K->55945K(599040K), 0.3522740 secs] 1694537K->1214361K(3005440K), 0.3527210 secs]

我的服务器没有访问压力，为什么一次Minor GC需要0.x秒？我相信一次 Minor GC 的花费应该少于 0.1 秒。

由于newRation的默认值是8，我应该将-Xmn650m更改为-Xmn350m吗？我不确定。

Answer 1

我不明白你为什么担心 0.3 秒的小收集。

如果您确实想减少次要收集时间，那么减少新空间的大小就可以做到这一点。但是，它可能会产生副作用，即提高对象的保有率，并导致主要收集更频繁地发生。