每隔一小时发现Full GC (System)

540730.747: [GC [PSYoungGen: 40128K->784K(41856K)] 72340K->32996K(129280K), 0.0039860 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
541382.310: [GC [PSYoungGen: 40912K->464K(42048K)] 73124K->33448K(129472K), 0.0260190 secs] [Times: user=0.00 sys=0.00, real=0.02 secs]
542032.458: [GC [PSYoungGen: 40848K->64K(41984K)] 73832K->33460K(129408K), 0.0025640 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
542682.532: [GC [PSYoungGen: 40448K->64K(42048K)] 73844K->33464K(129472K), 0.0018380 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
543332.610: [GC [PSYoungGen: 40512K->64K(42048K)] 73912K->33468K(129472K), 0.0018120 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
543679.124: [GC [PSYoungGen: 21924K->64K(42048K)] 55328K->33472K(129472K), 0.0026790 secs] [Times: user=0.01 sys=0.00, real=0.00 secs]
543679.127: [Full GC (System) [PSYoungGen: 64K->0K(42048K)] [PSOldGen: 33408K->32208K(87424K)] 33472K->32208K(129472K) [PSPermGen: 34262K->34252K(196608K)], 0.6865090 secs] [Times: user=0.20 sys=0.01, real=0.69 secs]
544334.031: [GC [PSYoungGen: 40448K->930K(41408K)] 72656K->33139K(128832K), 0.0042290 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
544992.803: [GC [PSYoungGen: 41378K->832K(41984K)] 73587K->33959K(129408K), 0.0055140 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
545644.774: [GC [PSYoungGen: 41152K->866K(41984K)] 74279K->34818K(129408K), 0.0116930 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
546293.006: [GC [PSYoungGen: 41186K->880K(41984K)] 75138K->35686K(129408K), 0.0056190 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
546943.104: [GC [PSYoungGen: 41200K->752K(41984K)] 76006K->36426K(129408K), 0.0052400 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
547279.826: [GC [PSYoungGen: 21736K->496K(42112K)] 57410K->36914K(129536K), 0.0215490 secs] [Times: user=0.00 sys=0.00, real=0.03 secs]
547279.848: [Full GC (System) [PSYoungGen: 496K->0K(42112K)] [PSOldGen: 36418K->36458K(87424K)] 36914K->36458K(129536K) [PSPermGen: 34252K->34252K(196608K)], 1.4649770 secs] [Times: user=0.21 sys=0.00, real=1.46 secs]
547783.324: [GC [PSYoungGen: 40512K->1520K(40960K)] 76970K->41408K(128384K), 0.0147620 secs] [Times: user=0.01 sys=0.00, real=0.02 secs]
548406.389: [GC [PSYoungGen: 40944K->1200K(39360K)] 80832K->42605K(126784K), 0.0077160 secs] [Times: user=0.01 sys=0.00, real=0.00 secs]
549023.518: [GC [PSYoungGen: 38960K->816K(40704K)] 80365K->43411K(128128K), 0.0082390 secs] [Times: user=0.01 sys=0.00, real=0.00 secs]
549633.616: [GC [PSYoungGen: 38576K->850K(41024K)] 81171K->44257K(128448K), 0.0058130 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
550257.604: [GC [PSYoungGen: 39122K->880K(40896K)] 82529K->45125K(128320K), 0.0056370 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
550873.787: [GC [PSYoungGen: 39152K->800K(41280K)] 83397K->45913K(128704K), 0.0648560 secs] [Times: user=0.01 sys=0.00, real=0.07 secs]
550881.328: [GC [PSYoungGen: 1583K->48K(41152K)] 46697K->45949K(128576K), 0.1452710 secs] [Times: user=0.00 sys=0.00, real=0.14 secs]
550881.474: [Full GC (System) [PSYoungGen: 48K->0K(41152K)] [PSOldGen: 45901K->38608K(87424K)] 45949K->38608K(128576K) [PSPermGen: 34264K->34264K(196608K)], 0.9540510 secs] [Times: user=0.22 sys=0.00, real=0.95 secs]
551509.968: [GC [PSYoungGen: 38784K->832K(41344K)] 77392K->39440K(128768K), 0.0043530 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
552148.793: [GC [PSYoungGen: 39744K->848K(41216K)] 78352K->40276K(128640K), 0.0056430 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
552769.888: [GC [PSYoungGen: 39760K->866K(41600K)] 79188K->41130K(129024K), 0.0054880 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
553419.542: [GC [PSYoungGen: 40290K->848K(41472K)] 80554K->41966K(128896K), 0.0057560 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
554051.009: [GC [PSYoungGen: 40272K->816K(41792K)] 81390K->42770K(129216K), 0.0055220 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
554482.429: [GC [PSYoungGen: 28138K->528K(41728K)] 70093K->43270K(129152K), 0.0066440 secs] [Times: user=0.01 sys=0.00, real=0.00 secs]
554482.435: [Full GC (System) [PSYoungGen: 528K->0K(41728K)] [PSOldGen: 42742K->32971K(87424K)] 43270K->32971K(129152K) [PSPermGen: 34266K->34266K(196608K)], 0.2227970 secs] [Times: user=0.18 sys=0.01, real=0.23 secs]
555130.613: [GC [PSYoungGen: 39872K->704K(41920K)] 72843K->33675K(129344K), 0.0036940 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
555780.862: [GC [PSYoungGen: 40832K->720K(41856K)] 73803K->34363K(129280K), 0.0049360 secs] [Times: user=0.01 sys=0.00, real=0.00 secs]
556421.417: [GC [PSYoungGen: 40848K->818K(42048K)] 74491K->35169K(129472K), 0.0056240 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
557074.632: [GC [PSYoungGen: 41202K->736K(41984K)] 75553K->35841K(129408K), 0.0055060 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
557732.214: [GC [PSYoungGen: 41120K->656K(42176K)] 76225K->36493K(129600K), 0.0064320 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]
558082.659: [GC [PSYoungGen: 22619K->368K(42112K)] 58457K->36853K(129536K), 0.0066010 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
558082.666: [Full GC (System) [PSYoungGen: 368K->0K(42112K)] [PSOldGen: 36485K->32282K(87424K)] 36853K->32282K(129536K) [PSPermGen: 34270K->34252K(196608K)], 0.2997530 secs]



以上是我服务器tomcat中的gc信息，我发现每隔一个小时(3600s)，就会出现一个full gc，而且有个system字样。这是不是说明程序中显示调用了System.gc？
我看了一下每次full gc的时间都在0.2s左右，但现在最高居然到了1.4s，太恐怖了！对于WEB应用来说，1.4S意味着什么！！！

你的堆内存是不是设置的过小了？

请参考之前一帖的第二点：http://hllvm.group.iteye.com/group/topic/27945
可以通过调大-Dsun.rmi.dgc.client.gcInterval=参数来增大RMI触发System GC的间隔。你的GC是ParallelGC所以就用不了-XX:+ExplicitGCInvokesConcurrent之类的别的选择了。

撒迦的回复基本是权威了

应该是程序里显式调用了System.gc(),从[Full GC (System) 判断。
通过配置参数 -XX:+ DisableExplicitGC 可以禁止掉。