hotspot垃圾收集器
测试代码
使用serial + serial Old
full gc通过(System.gc())触发
年轻代垃垃圾收集器名字 DefNew
老年代Tenured 持久带 Perm
年轻代收集过程
从jstat看，只触发了YGC
老年代和持久带的收集过程
只触发了FGC，但是却没有YGC
如果开启Syste.gc()，也是一样，只有FGC，没有YGC
Parallel Scavenge +Parallel Old 组合显示的结果，full gc通过(System.gc())触发，
年轻代收集器名称 PSYoungGen
老年代ParOldGen， 持久带PSPermGen
年轻代的收集过程，只触发YGC
通过程序触发的full gc，此时YGC，FGC都会触发
Parallel GC的线程名
使用ParNew + ConcMarkSweep ，full gc通过(System.gc())触发，
ParNew GC的线程名
CMS线程名
年轻代收集过程，此时只会触发YGC
老年代和持久带收集过程，只会触发FGC
通过System.gc()触发，此时只有FGC，没有YGC
CMS中有，初始化，并发标记，重新标记，并发清除几个阶段
以下是初始化，并发标记
重新标记，并发清除
此外还有扫描中断：
处理失败的情况，此时使用serial old：
最后是G1，其线程名如下：
清扫过程：由于G1不能很好的和jstat配合工作，因此看不到gcutil情况
jdk1.7.0_04 打开G1，jstat，jmap等工具可以正常使用。
public void test()throws Exception {
while(true) {
byte[] buf = new byte[3 * 1024 * 1024];
Thread.sleep(500);
//System.gc();
}
}
使用serial + serial Old
full gc通过(System.gc())触发
年轻代垃垃圾收集器名字 DefNew
老年代Tenured 持久带 Perm
年轻代收集过程
C:\>java -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:+ScavengeBeforeFullGC -
XX:+UseSerialGC Test2
[GC [DefNew: 6471K->146K(9216K), 0.0043318 secs] 6471K->146K(19456K), 0.0053627
secs] [Times: user=0.00 sys=0.02, real=0.01 secs]
[GC [DefNew: 6540K->146K(9216K), 0.0022464 secs] 6540K->146K(19456K), 0.0032348
secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
Heap
def new generation total 9216K, used 3546K [0x315e0000, 0x31fe0000, 0x31fe000
0)
eden space 8192K, 41% used [0x315e0000, 0x31931f28, 0x31de0000)
from space 1024K, 14% used [0x31de0000, 0x31e04920, 0x31ee0000)
to space 1024K, 0% used [0x31ee0000, 0x31ee0000, 0x31fe0000)
tenured generation total 10240K, used 0K [0x31fe0000, 0x329e0000, 0x329e0000)
the space 10240K, 0% used [0x31fe0000, 0x31fe0000, 0x31fe0200, 0x329e0000)
compacting perm gen total 12288K, used 374K [0x329e0000, 0x335e0000, 0x369e000
0)
the space 12288K, 3% used [0x329e0000, 0x32a3dba0, 0x32a3dc00, 0x335e0000)
ro space 10240K, 54% used [0x369e0000, 0x36f5ee00, 0x36f5ee00, 0x373e0000)
rw space 12288K, 55% used [0x373e0000, 0x37a82800, 0x37a82800, 0x37fe0000)
从jstat看，只触发了YGC
C:\>jstat -gcutil 2528 1000 20 S0 S1 E O P YGC YGCT FGC FGCT GCT 14.29 0.00 37.50 0.00 3.04 12 0.029 0 0.000 0.029 0.00 14.29 37.50 0.00 3.04 13 0.032 0 0.000 0.032 14.29 0.00 37.50 0.00 3.04 14 0.034 0 0.000 0.034 0.00 14.29 37.50 0.00 3.04 15 0.036 0 0.000 0.036 0.01 0.00 37.50 1.43 3.04 16 0.038 0 0.000 0.038 0.00 0.00 37.50 1.43 3.04 17 0.040 0 0.000 0.040 0.00 0.00 37.50 1.43 3.04 18 0.041 0 0.000 0.041 0.00 0.00 37.50 1.43 3.04 19 0.042 0 0.000 0.042 0.00 0.00 37.50 1.43 3.04 20 0.043 0 0.000 0.043 0.00 0.00 37.50 1.43 3.04 21 0.044 0 0.000 0.044 0.00 0.00 37.50 1.43 3.04 22 0.044 0 0.000 0.044
老年代和持久带的收集过程
C:\>java -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:+ScavengeBeforeFullGC -
XX:PretenureSizeThreshold=2097152 -XX:+UseSerialGC Test2
[GC [Tenured: 9216K->146K(10240K), 0.0310260 secs] 9543K->146K(19456K), [Perm :
373K->373K(12288K)], 0.0322100 secs] [Times: user=0.03 sys=0.00, real=0.03 secs]
[GC [Tenured: 9362K->146K(10240K), 0.0238268 secs] 12762K->146K(19456K), [Perm :
373K->373K(12288K)], 0.0256443 secs] [Times: user=0.02 sys=0.00, real=0.01 secs
]
Heap
def new generation total 9216K, used 3563K [0x315e0000, 0x31fe0000, 0x31fe000
0)
eden space 8192K, 43% used [0x315e0000, 0x3195ae88, 0x31de0000)
from space 1024K, 0% used [0x31de0000, 0x31de0000, 0x31ee0000)
to space 1024K, 0% used [0x31ee0000, 0x31ee0000, 0x31fe0000)
tenured generation total 10240K, used 3218K [0x31fe0000, 0x329e0000, 0x329e00
00)
the space 10240K, 31% used [0x31fe0000, 0x32304a00, 0x32304a00, 0x329e0000)
compacting perm gen total 12288K, used 374K [0x329e0000, 0x335e0000, 0x369e000
0)
the space 12288K, 3% used [0x329e0000, 0x32a3dba0, 0x32a3dc00, 0x335e0000)
ro space 10240K, 54% used [0x369e0000, 0x36f5ee00, 0x36f5ee00, 0x373e0000)
rw space 12288K, 55% used [0x373e0000, 0x37a82800, 0x37a82800, 0x37fe0000)
只触发了FGC，但是却没有YGC
C:\>jstat -gcutil 2572 1000 20 S0 S1 E O P YGC YGCT FGC FGCT GCT 0.00 0.00 39.50 31.43 3.04 0 0.000 23 0.621 0.621 0.00 0.00 39.50 31.43 3.04 0 0.000 25 0.675 0.675 0.00 0.00 39.50 31.43 3.04 0 0.000 27 0.728 0.728 0.00 0.00 39.50 31.43 3.04 0 0.000 29 0.782 0.782 0.00 0.00 39.50 31.43 3.04 0 0.000 31 0.837 0.837 0.00 0.00 39.50 31.30 3.00 0 0.000 33 0.891 0.891
如果开启Syste.gc()，也是一样，只有FGC，没有YGC
C:\>java -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:+ScavengeBeforeFullGC -
XX:PretenureSizeThreshold=2097152 -XX:+UseSerialGC Test2
[Full GC (System) [Tenured: 3072K->3218K(10240K), 0.0281815 secs] 3399K->3218K(1
9456K), [Perm : 373K->373K(12288K)], 0.0297979 secs] [Times: user=0.03 sys=0.00,
real=0.03 secs]
[Full GC (System) [Tenured: 3218K->3218K(10240K), 0.0269135 secs] 6618K->3218K(1
9456K), [Perm : 373K->373K(12288K)], 0.0280661 secs] [Times: user=0.02 sys=0.00,
real=0.03 secs]
Heap
def new generation total 9216K, used 3563K [0x315e0000, 0x31fe0000, 0x31fe000
0)
eden space 8192K, 43% used [0x315e0000, 0x3195ae88, 0x31de0000)
from space 1024K, 0% used [0x31de0000, 0x31de0000, 0x31ee0000)
to space 1024K, 0% used [0x31ee0000, 0x31ee0000, 0x31fe0000)
tenured generation total 10240K, used 3218K [0x31fe0000, 0x329e0000, 0x329e00
00)
the space 10240K, 31% used [0x31fe0000, 0x32304930, 0x32304a00, 0x329e0000)
compacting perm gen total 12288K, used 374K [0x329e0000, 0x335e0000, 0x369e000
0)
the space 12288K, 3% used [0x329e0000, 0x32a3dbd8, 0x32a3dc00, 0x335e0000)
ro space 10240K, 54% used [0x369e0000, 0x36f5ee00, 0x36f5ee00, 0x373e0000)
rw space 12288K, 55% used [0x373e0000, 0x37a82800, 0x37a82800, 0x37fe0000)
C:\>jstat -gcutil 3724 1000 20 S0 S1 E O P YGC YGCT FGC FGCT GCT 0.00 0.00 0.00 31.43 3.04 0 0.000 20 0.535 0.535 0.00 0.00 39.50 31.43 3.04 0 0.000 21 0.551 0.551 0.00 0.00 39.50 31.43 3.04 0 0.000 23 0.604 0.604 0.00 0.00 39.50 31.43 3.04 0 0.000 25 0.659 0.659 0.00 0.00 39.50 31.43 3.04 0 0.000 27 0.715 0.715 0.00 0.00 39.50 31.43 3.04 0 0.000 29 0.768 0.768 0.00 0.00 39.50 31.43 3.04 0 0.000 31 0.823 0.823
Parallel Scavenge +Parallel Old 组合显示的结果，full gc通过(System.gc())触发，
年轻代收集器名称 PSYoungGen
老年代ParOldGen， 持久带PSPermGen
年轻代的收集过程，只触发YGC
C:\>java -Xmx15M -Xms15M -Xmn10M -XX:+PrintGCDetails -XX:+ScavengeBeforeFullGC - XX:PretenureSizeThreshold=2097152 -XX:+UseParallelOldGC -XX:ParallelGCThreads=10 Test2 [GC [PSYoungGen: 4419K->176K(8960K)] 8515K->4272K(15104K), 0.0034451 secs] [Time s: user=0.03 sys=0.00, real=0.02 secs] [GC [PSYoungGen: 4425K->168K(8960K)] 8521K->4264K(15104K), 0.0032476 secs] [Time s: user=0.00 sys=0.00, real=0.00 secs] Heap PSYoungGen total 8960K, used 4571K [0x06ff0000, 0x079f0000, 0x079f0000) eden space 7680K, 57% used [0x06ff0000,0x0743cd38,0x07770000) from space 1280K, 13% used [0x078b0000,0x078da030,0x079f0000) to space 1280K, 0% used [0x07770000,0x07770000,0x078b0000) ParOldGen total 6144K, used 4096K [0x069f0000, 0x06ff0000, 0x06ff0000) object space 6144K, 66% used [0x069f0000,0x06df0010,0x06ff0000) PSPermGen total 12288K, used 2104K [0x029f0000, 0x035f0000, 0x069f0000) object space 12288K, 17% used [0x029f0000,0x02bfe3c8,0x035f0000)
通过程序触发的full gc，此时YGC，FGC都会触发
C:\>java -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:-ScavengeBeforeFullGC -XX:PretenureSizeThreshold=2097152 -XX:+UseParallelOldGC Test2 [Full GC (System) [PSYoungGen: 3395K->0K(8960K)] [ParOldGen: 0K->3218K(10240K)] 3395K->3218K(19200K) [PSPermGen: 2091K->2091K(12288K)], 0.0317060 secs] [Times: user=0.05 sys=0.00, real=0.03 secs] [Full GC (System) [PSYoungGen: 3379K->0K(8960K)] [ParOldGen: 3218K->3218K(10240K )] 6597K->3218K(19200K) [PSPermGen: 2097K->2097K(12288K)], 0.0238544 secs] [Time s: user=0.01 sys=0.00, real=0.02 secs] [Full GC (System) [PSYoungGen: 3225K->0K(8960K)] [ParOldGen: 3218K->3218K(10240K )] 6443K->3218K(19200K) [PSPermGen: 2097K->2097K(12288K)], 0.0254747 secs] [Time s: user=0.02 sys=0.00, real=0.02 secs] Heap PSYoungGen total 8960K, used 3532K [0x073f0000, 0x07df0000, 0x07df0000) eden space 7680K, 46% used [0x073f0000,0x077633a0,0x07b70000) from space 1280K, 0% used [0x07cb0000,0x07cb0000,0x07df0000) to space 1280K, 0% used [0x07b70000,0x07b70000,0x07cb0000) ParOldGen total 10240K, used 3218K [0x069f0000, 0x073f0000, 0x073f0000) object space 10240K, 31% used [0x069f0000,0x06d14928,0x073f0000) PSPermGen total 12288K, used 2104K [0x029f0000, 0x035f0000, 0x069f0000) object space 12288K, 17% used [0x029f0000,0x02bfe108,0x035f0000)
Parallel GC的线程名
"GC task thread#0 (ParallelGC)" prio=6 tid=0x0031e000 nid=0x988 runnable
使用ParNew + ConcMarkSweep ，full gc通过(System.gc())触发，
ParNew GC的线程名
"Gang worker#0 (Parallel GC Threads)" prio=10 tid=0x0031bc00 nid=0x604 runnable
CMS线程名
"Concurrent Mark-Sweep GC Thread" prio=10 tid=0x0836e400 nid=0xe18 runnable "Gang worker#0 (Parallel CMS Threads)" prio=10 tid=0x082cc000 nid=0xd18 runnable
年轻代收集过程，此时只会触发YGC
C:\>java -Xmx20M -Xms20M -Xmn10M -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -X X:ParallelGCThreads=10 Test2 [GC [ParNew: 4423K->168K(9216K), 0.0055490 secs] 4423K->168K(19456K), 0.0062150 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] [GC [ParNew: 4428K->176K(9216K), 0.0032652 secs] 4428K->176K(19456K), 0.0044014 secs] [Times: user=0.03 sys=0.00, real=0.02 secs] Heap par new generation total 9216K, used 4600K [0x02e10000, 0x03810000, 0x0381000 0) eden space 8192K, 54% used [0x02e10000, 0x03261f28, 0x03610000) from space 1024K, 17% used [0x03610000, 0x0363c3c0, 0x03710000) to space 1024K, 0% used [0x03710000, 0x03710000, 0x03810000) concurrent mark-sweep generation total 10240K, used 0K [0x03810000, 0x04210000, 0x04210000) concurrent-mark-sweep perm gen total 12288K, used 2104K [0x04210000, 0x04e10000 , 0x08210000)
老年代和持久带收集过程，只会触发FGC
C:\>java -Xmx20M -Xms20M -Xmn10M -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -X X:ParallelGCThreads=10 -XX:PretenureSizeThreshold=2097152 Test2 [GC [CMS: 8192K->146K(10240K), 0.0272448 secs] 8519K->146K(19456K), [CMS Perm : 2091K->2091K(12288K)], 0.0294118 secs] [Times: user=0.01 sys=0.02, real=0.03 sec s] [GC [CMS: 8338K->146K(10240K), 0.0229166 secs] 12762K->146K(19456K), [CMS Perm : 2097K->2097K(12288K)], 0.0248618 secs] [Times: user=0.01 sys=0.00, real=0.01 se cs] [GC [1 CMS-initial-mark: 8338K(10240K)] 12519K(19456K), 0.0010387 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] [CMS-concurrent-mark: 0.009/0.009 secs] [Times: user=0.03 sys=0.00, real=0.02 se cs] [CMS-concurrent-preclean: 0.000/0.000 secs] [Times: user=0.00 sys=0.00, real=0.0 0 secs] [GC [CMS[CMS-concurrent-abortable-preclean: 0.000/0.035 secs] [Times: user=0.00 sys=0.00, real=0.03 secs] (concurrent mode failure): 8338K->146K(10240K), 0.0236156 secs] 12519K->146K(19 456K), [CMS Perm : 2097K->2097K(12288K)], 0.0257522 secs] [Times: user=0.02 sys= 0.00, real=0.03 secs] [GC [CMS: 8338K->146K(10240K), 0.0213714 secs] 12491K->146K(19456K), [CMS Perm : 2097K->2097K(12288K)], 0.0231105 secs] [Times: user=0.03 sys=0.00, real=0.03 se cs] [GC [CMS: 8338K->146K(10240K), 0.0224847 secs] 12472K->146K(19456K), [CMS Perm : 2097K->2097K(12288K)], 0.0243117 secs] [Times: user=0.03 sys=0.00, real=0.03 se cs] [GC [CMS: 8338K->146K(10240K), 0.0219254 secs] 12459K->146K(19456K), [CMS Perm : 2097K->2097K(12288K)], 0.0242763 secs] [Times: user=0.02 sys=0.01, real=0.03 se cs] Heap par new generation total 9216K, used 4440K [0x02e10000, 0x03810000, 0x0381000 0) eden space 8192K, 54% used [0x02e10000, 0x03266128, 0x03610000) from space 1024K, 0% used [0x03610000, 0x03610000, 0x03710000) to space 1024K, 0% used [0x03710000, 0x03710000, 0x03810000) concurrent mark-sweep generation total 10240K, used 4242K [0x03810000, 0x042100 00, 0x04210000) concurrent-mark-sweep perm gen total 12288K, used 2104K [0x04210000, 0x04e10000 , 0x08210000)
通过System.gc()触发，此时只有FGC，没有YGC
C:\>java -Xmx20M -Xms20M -Xmn10M -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -X X:ParallelGCThreads=10 -XX:PretenureSizeThreshold=2097152 -XX:+ScavengeBeforeFul lGC Test2 [Full GC (System) [CMS: 4096K->4242K(10240K), 0.0274647 secs] 4423K->4242K(19456 K), [CMS Perm : 2091K->2091K(12288K)], 0.0289805 secs] [Times: user=0.03 sys=0.0 0, real=0.03 secs] [Full GC (System) [CMS: 4242K->4242K(10240K), 0.0256547 secs] 8666K->4242K(19456 K), [CMS Perm : 2097K->2097K(12288K)], 0.0265903 secs] [Times: user=0.02 sys=0.0 0, real=0.02 secs] [Full GC (System) [CMS: 4242K->4242K(10240K), 0.0258008 secs] 8423K->4242K(19456 K), [CMS Perm : 2097K->2097K(12288K)], 0.0271459 secs] [Times: user=0.02 sys=0.0 0, real=0.01 secs] Heap par new generation total 9216K, used 4480K [0x02e10000, 0x03810000, 0x0381000 0) eden space 8192K, 54% used [0x02e10000, 0x032700b0, 0x03610000) from space 1024K, 0% used [0x03610000, 0x03610000, 0x03710000) to space 1024K, 0% used [0x03710000, 0x03710000, 0x03810000) concurrent mark-sweep generation total 10240K, used 4242K [0x03810000, 0x042100 00, 0x04210000) concurrent-mark-sweep perm gen total 12288K, used 2104K [0x04210000, 0x04e10000 , 0x08210000)
CMS中有，初始化，并发标记，重新标记，并发清除几个阶段
以下是初始化，并发标记
C:\>java -Xmx15M -Xms15M -Xmn10M -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -X X:ParallelGCThreads=10 -XX:PretenureSizeThreshold=2097152 -XX:+ScavengeBeforeFul lGC Test2
[GC [1 CMS-initial-mark: 4242K(6144K)] 4242K(15360K), 0.0007012 secs] [Times: us er=0.00 sys=0.00, real=0.00 secs] [CMS-concurrent-mark: 0.009/0.009 secs] [Times: user=0.02 sys=0.01, real=0.02 se cs]
重新标记，并发清除
[GC[YG occupancy: 4106 K (9216 K)][Rescan (parallel) , 0.0013488 secs][weak refs processing, 0.0000218 secs] [1 CMS-remark: 4242K(6144K)] 8349K(15360K), 0.00288 98 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] [CMS-concurrent-sweep: 0.000/0.000 secs] [Times: user=0.01 sys=0.00, real=0.01 s ecs] [CMS-concurrent-reset: 0.001/0.001 secs] [Times: user=0.00 sys=0.00, real=0.00 s ecs]
此外还有扫描中断：
[Full GC (System) [CMS[CMS-concurrent-abortable-preclean: 0.001/0.499 secs] [Tim es: user=0.00 sys=0.00, real=0.50 secs] (concurrent mode interrupted): 4242K->4242K(6144K), 0.0266688 secs] 8363K->4242 K(15360K), [CMS Perm : 2097K->2097K(12288K)], 0.0283159 secs] [Times: user=0.03 sys=0.00, real=0.03 secs]
处理失败的情况，此时使用serial old：
(concurrent mode failure): 8338K->146K(10240K), 0.0260159 secs] 12519K->146K(19 456K), [CMS Perm : 2097K->2097K(12288K)], 0.0277560 secs] [Times: user=0.02 sys= 0.01, real=0.03 secs]
最后是G1，其线程名如下：
"Gang worker#0 (Parallel GC Threads)" prio=10 tid=0x08a4f800 nid=0x108d runnable "G1 Main Concurrent Mark GC Thread" prio=10 tid=0x08a6a400 nid=0x1090 runnable "Gang worker#0 (G1 Parallel Marking Threads)" prio=10 tid=0x08a7bc00 nid=0x1091 runnable "G1 Concurrent Refinement Thread#0" prio=10 tid=0x08a62800 nid=0x108f runnable "G1 Concurrent Refinement Thread#1" prio=10 tid=0x08a61000 nid=0x108e runnable
清扫过程：由于G1不能很好的和jstat配合工作，因此看不到gcutil情况
[GC pause (young), 0.00875300 secs]
[Parallel Time: 8.6 ms]
[GC Worker Start Time (ms): 19253.4]
[Update RS (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Processed Buffers : 0
Sum: 0, Avg: 0, Min: 0, Max: 0]
[Ext Root Scanning (ms): 7.5
Avg: 7.5, Min: 7.5, Max: 7.5]
[Mark Stack Scanning (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Scan RS (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Object Copy (ms): 0.1
Avg: 0.1, Min: 0.1, Max: 0.1]
[Termination (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Termination Attempts : 1
Sum: 1, Avg: 1, Min: 1, Max: 1]
[GC Worker End Time (ms): 19261.2]
[Other: 0.9 ms]
[Clear CT: 0.0 ms]
[Other: 0.1 ms]
[Choose CSet: 0.0 ms]
[ 12M->12M(20M)]
[Times: user=0.00 sys=0.00, real=0.01 secs]
[Full GC 12M->114K(20M), 0.0280980 secs]
[Times: user=0.02 sys=0.00, real=0.02 secs]
[GC pause (young), 0.00837900 secs]
[Parallel Time: 8.1 ms]
[GC Worker Start Time (ms): 21412.9]
[Update RS (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Processed Buffers : 0
Sum: 0, Avg: 0, Min: 0, Max: 0]
[Ext Root Scanning (ms): 6.8
Avg: 6.8, Min: 6.8, Max: 6.8]
[Mark Stack Scanning (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Scan RS (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Object Copy (ms): 0.1
Avg: 0.1, Min: 0.1, Max: 0.1]
[Termination (ms): 0.0
Avg: 0.0, Min: 0.0, Max: 0.0]
[Termination Attempts : 1
Sum: 1, Avg: 1, Min: 1, Max: 1]
[GC Worker End Time (ms): 21419.9]
[Other: 1.1 ms]
[Clear CT: 0.1 ms]
[Other: 0.1 ms]
[Choose CSet: 0.0 ms]
[ 12M->12M(20M)]
[Times: user=0.00 sys=0.00, real=0.01 secs]
[Full GC 12M->101K(20M), 0.0368190 secs]
[Times: user=0.04 sys=0.00, real=0.02 secs]
Heap
garbage-first heap total 20480K, used 8293K [0xaff00000, 0xb1300000, 0xb1300000)
region size 1024K, 1 young (1024K), 0 survivors (0K)
compacting perm gen total 12288K, used 1724K [0xb1300000, 0xb1f00000, 0xb5300000)
the space 12288K, 14% used [0xb1300000, 0xb14af300, 0xb14af400, 0xb1f00000)
No shared spaces configured.
jdk1.7.0_04 打开G1，jstat，jmap等工具可以正常使用。
C:\jdk1.7.0_04\bin>java -Xmx20M -Xms20M -Xmn10M -XX:+UseG1GC -XX:+PrintGCDet
ails Test2
[GC pause (young) (initial-mark), 0.00661676 secs]
[Parallel Time: 5.7 ms]
[GC Worker Start (ms): 747.9 747.9
Avg: 747.9, Min: 747.9, Max: 747.9, Diff: 0.0]
[Ext Root Scanning (ms): 2.1 1.9
Avg: 2.0, Min: 1.9, Max: 2.1, Diff: 0.2]
[Update RS (ms): 0.0 0.1
Avg: 0.1, Min: 0.0, Max: 0.1, Diff: 0.1]
[Processed Buffers : 0 5
Sum: 5, Avg: 2, Min: 0, Max: 5, Diff: 5]
[Scan RS (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Object Copy (ms): 3.3 3.3
Avg: 3.3, Min: 3.3, Max: 3.3, Diff: 0.1]
[Termination (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Termination Attempts : 1 1
Sum: 2, Avg: 1, Min: 1, Max: 1, Diff: 0]
[GC Worker End (ms): 753.4 753.4
Avg: 753.4, Min: 753.4, Max: 753.4, Diff: 0.0]
[GC Worker (ms): 5.5 5.5
Avg: 5.5, Min: 5.5, Max: 5.5, Diff: 0.0]
[GC Worker Other (ms): 0.3 0.3
Avg: 0.3, Min: 0.3, Max: 0.3, Diff: 0.0]
[Clear CT: 0.0 ms]
[Other: 0.9 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 0.1 ms]
[Ref Enq: 0.0 ms]
[Free CSet: 0.0 ms]
[Eden: 1024K(10M)->0B(9216K) Survivors: 0B->1024K Heap: 4663K(20M)->4560K(20M
)]
[Times: user=0.03 sys=0.00, real=0.02 secs]
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0019206]
[GC concurrent-mark-start]
[GC concurrent-mark-end, 0.0012521 sec]
[GC remark [GC ref-proc, 0.0000235 secs], 0.0031993 secs]
[Times: user=0.00 sys=0.00, real=0.00 secs]
[GC cleanup 8697K->4601K(20M), 0.0008915 secs]
[Times: user=0.00 sys=0.02, real=0.02 secs]
[GC concurrent-cleanup-start]
[GC concurrent-cleanup-end, 0.0004232]
[GC pause (young) (initial-mark), 0.00516323 secs]
[Parallel Time: 4.3 ms]
[GC Worker Start (ms): 1281.0 1281.0
Avg: 1281.0, Min: 1281.0, Max: 1281.0, Diff: 0.0]
[Ext Root Scanning (ms): 1.5 1.4
Avg: 1.4, Min: 1.4, Max: 1.5, Diff: 0.1]
[Update RS (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Processed Buffers : 0 2
Sum: 2, Avg: 1, Min: 0, Max: 2, Diff: 2]
[Scan RS (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Object Copy (ms): 2.7 2.7
Avg: 2.7, Min: 2.7, Max: 2.7, Diff: 0.0]
[Termination (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Termination Attempts : 1 1
Sum: 2, Avg: 1, Min: 1, Max: 1, Diff: 0]
[GC Worker End (ms): 1285.2 1285.2
Avg: 1285.2, Min: 1285.2, Max: 1285.2, Diff: 0.0]
[GC Worker (ms): 4.2 4.2
Avg: 4.2, Min: 4.2, Max: 4.2, Diff: 0.0]
[GC Worker Other (ms): 0.1 0.1
Avg: 0.1, Min: 0.1, Max: 0.1, Diff: 0.0]
[Clear CT: 0.0 ms]
[Other: 0.9 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 0.1 ms]
[Ref Enq: 0.0 ms]
[Free CSet: 0.0 ms]
[Eden: 1024K(9216K)->0B(9216K) Survivors: 1024K->1024K Heap: 4601K(20M)->4544
K(20M)]
[Times: user=0.03 sys=0.00, real=0.03 secs]
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0016821]
[GC concurrent-mark-start]
[GC concurrent-mark-end, 0.0005808 sec]
[GC remark [GC ref-proc, 0.0000212 secs], 0.0029291 secs]
[Times: user=0.00 sys=0.00, real=0.00 secs]
[GC cleanup 8640K->4544K(20M), 0.0008895 secs]
[Times: user=0.00 sys=0.00, real=0.02 secs]
[GC concurrent-cleanup-start]
[GC concurrent-cleanup-end, 0.0005897]
[GC pause (young) (initial-mark), 0.00520737 secs]
[Parallel Time: 4.3 ms]
[GC Worker Start (ms): 1812.2 1812.2
Avg: 1812.2, Min: 1812.2, Max: 1812.2, Diff: 0.0]
[Ext Root Scanning (ms): 1.5 1.3
Avg: 1.4, Min: 1.3, Max: 1.5, Diff: 0.2]
[Update RS (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Processed Buffers : 0 0
Sum: 0, Avg: 0, Min: 0, Max: 0, Diff: 0]
[Scan RS (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Object Copy (ms): 2.6 2.8
Avg: 2.7, Min: 2.6, Max: 2.8, Diff: 0.2]
[Termination (ms): 0.0 0.0
Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0]
[Termination Attempts : 1 1
Sum: 2, Avg: 1, Min: 1, Max: 1, Diff: 0]
[GC Worker End (ms): 1816.4 1816.4
Avg: 1816.4, Min: 1816.4, Max: 1816.4, Diff: 0.0]
[GC Worker (ms): 4.2 4.2
Avg: 4.2, Min: 4.2, Max: 4.2, Diff: 0.0]
[GC Worker Other (ms): 0.1 0.1
Avg: 0.1, Min: 0.1, Max: 0.1, Diff: 0.0]
[Clear CT: 0.0 ms]
[Other: 0.9 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 0.1 ms]
[Ref Enq: 0.0 ms]
[Free CSet: 0.0 ms]
[Eden: 0B(9216K)->0B(9216K) Survivors: 1024K->1024K Heap: 4544K(20M)->4544K(2
0M)]
[Times: user=0.03 sys=0.00, real=0.03 secs]
[GC concurrent-root-region-scan-start]
[GC concurrent-root-region-scan-end, 0.0014873]
[GC concurrent-mark-start]
[GC concurrent-mark-end, 0.0006668 sec]
[GC remark [GC ref-proc, 0.0000263 secs], 0.0028615 secs]
[Times: user=0.00 sys=0.00, real=0.00 secs]
[GC cleanup 8640K->4544K(20M), 0.0007965 secs]
[Times: user=0.00 sys=0.00, real=0.00 secs]
[GC concurrent-cleanup-start]
[GC concurrent-cleanup-end, 0.0006168]
Heap
garbage-first heap total 20480K, used 4544K [0x02d00000, 0x04100000, 0x041000
00)
region size 1024K, 2 young (2048K), 1 survivors (1024K)
compacting perm gen total 12288K, used 1572K [0x04100000, 0x04d00000, 0x081000
00)
the space 12288K, 12% used [0x04100000, 0x042893d0, 0x04289400, 0x04d00000)
No shared spaces configured.