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因为以前用默认的GC，，老年代经常在占比超过99%才发生一个GC行为，感觉不爽。。。尽管每次FULL GC只要0.5S。
结合上次听中华构架师大会，一哥们分享的G1 GC。。。试试。。
就在TOMCAT的catania.sh里JAVA的启动参数加一段吧。。
JAVA_OPTS=‘ -Xms512m -Xmx1024m -XX:PermSize=256M -XX:MaxNewSize=256m -XX:MaxPermSize=256m -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC ‘
JMAP输出如下啦：
jmap -heap xxxx Attaching to process ID xxx, please wait... Debugger attached successfully. Server compiler detected. JVM version is 24.0-b56 using thread-local object allocation. Garbage-First (G1) GC with 4 thread(s) Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 1073741824 (1024.0MB) NewSize = 1363144 (1.2999954223632812MB) MaxNewSize = 268435456 (256.0MB) OldSize = 5452592 (5.1999969482421875MB) NewRatio = 2 SurvivorRatio = 8 PermSize = 268435456 (256.0MB) MaxPermSize = 268435456 (256.0MB) G1HeapRegionSize = 1048576 (1.0MB) Heap Usage: G1 Heap: regions = 1024 capacity = 1073741824 (1024.0MB) used = 525790240 (501.4326477050781MB) free = 547951584 (522.5673522949219MB) 48.968032002449036% used G1 Young Generation: Eden Space: regions = 108 capacity = 275775488 (263.0MB) used = 113246208 (108.0MB) free = 162529280 (155.0MB) 41.06463878326996% used Survivor Space: regions = 6 capacity = 6291456 (6.0MB) used = 6291456 (6.0MB) free = 0 (0.0MB) 100.0% used G1 Old Generation: regions = 415 capacity = 791674880 (755.0MB) used = 406252576 (387.4326477050781MB) free = 385422304 (367.5673522949219MB) 51.31558247749379% used Perm Generation: capacity = 268435456 (256.0MB) used = 65695576 (62.652183532714844MB) free = 202739880 (193.34781646728516MB) 24.473509192466736% used 35236 interned Strings occupying 3876240 bytes.
JMAP相关GC输出如下：
jstat -gc xxxx 1000 10 S0C S1C S0U S1U EC EU OC OU PC PU YGC YGCT FGC FGCT GCT 0.0 6144.0 0.0 6144.0 269312.0 81920.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 100352.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 120832.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 139264.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 176128.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 193536.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 211968.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 229376.0 773120.0 396840.2 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 6144.0 0.0 6144.0 269312.0 243712.0 773120.0 400994.0 262144.0 64155.8 3579 84.690 0 0.000 84.690 0.0 8192.0 0.0 8192.0 267264.0 44032.0 773120.0 402843.3 262144.0 64155.8 3580 84.719 0 0.000 84.719
ZABBIX的输出图马上由大宝剑变成了蜿行蛇啦。。。
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原文地址：http://www.cnblogs.com/aguncn/p/4212780.html
