Java JVM GC问题
在过去的几周里，我一直在为我的Glassfish服务器测试不同的JVM设置。堆的主要设置（以及其他设置）是：-Xms512m，-Xmx512m，-XX:NewRatio=2。我尝试了不同的GC设置，但在启动服务器几天后仍然存在长时间暂停的问题。我注意到以下几点：Java JVM GC问题,java,garbage-collection,glassfish,jvm,Java,Garbage Collection,Glassfish,Jvm,在过去的几周里，我一直在为我的Glassfish服务器测试不同的JVM设置。堆的主要设置（以及其他设置）是：-Xms512m，-Xmx512m，-XX:NewRatio=2。我尝试了不同的GC设置，但在启动服务器几天后仍然存在长时间暂停的问题。我注意到以下几点： 1. -XX:+UseParallelGC-XX:+UseParallelOldGC-次要GC大约每分钟发生一次，主要GC每18小时发生一次。我没有小GC的问题，但在5天后有大GC的问题。最初主要GC暂停持续约100-200ms，但最后
1. -XX:+UseParallelGC-XX:+UseParallelOldGC-次要GC大约每分钟发生一次，主要GC每18小时发生一次。我没有小GC的问题，但在5天后有大GC的问题。最初主要GC暂停持续约100-200ms，但最后一次暂停持续70秒。
2. -XX:+useConMarkSweepGC-XX:+UseParNewGC-几乎与上面相同。次要GC正常，但主要GC（非完全）暂停时间变长。我注意到GC（CMS最终评论）阶段（停止世界阶段）的高级卸载存在问题。
3. -XX:+useConMarkSweepGC-XX:+UseParNewGC和-XX:MaxGCPauseMillis=5000。我只测试了一天，因为第二个主要GC last（未满）已经持续了大约20秒，所以我认为还有其他问题。
4. -XX:+UseG1GC，-XX:MaxGCPauseMillis=5000，-XX:+useStringDuplication不带-XX:NewRatio=2选项-主要GC（未满）每12小时发生一次，我已经注意到一些问题：
2015-05-31T18:25:25.145+0200: 83383.897: [GC concurrent-mark-start]
2015-05-31T18:25:35.563+0200: 83394.312: [GC concurrent-mark-end, 10.4145795 secs]
2015-05-31T18:25:35.563+0200: 83394.312: [GC remark 83394.312: [Finalize Marking, 0.0002939 secs] 83394.312: [GC ref-proc, 1.2128584 secs] 83395.525: [Unloading, 14.5180500 secs], 15.7320854 secs]
[Times: user=0.14 sys=0.22, real=15.73 secs]
2015-05-31T18:25:25.004+0200: 83383.755: [GC pause (G1 Evacuation Pause) (young) (initial-mark), 0.1280453 secs]
[Parallel Time: 116.2 ms, GC Workers: 4]
[GC Worker Start (ms): Min: 83383757.6, Avg: 83383757.7, Max: 83383757.7, Diff: 0.0]
[Ext Root Scanning (ms): Min: 97.8, Avg: 98.3, Max: 98.5, Diff: 0.7, Sum: 393.1]
[Update RS (ms): Min: 0.2, Avg: 4.0, Max: 14.8, Diff: 14.6, Sum: 16.1]
[Processed Buffers: Min: 1, Avg: 6.0, Max: 16, Diff: 15, Sum: 24]
[Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.1]
[Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Object Copy (ms): Min: 0.2, Avg: 2.5, Max: 3.7, Diff: 3.5, Sum: 10.2]
[Termination (ms): Min: 0.0, Avg: 8.5, Max: 11.4, Diff: 11.4, Sum: 34.2]
[GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[GC Worker Total (ms): Min: 113.4, Avg: 113.4, Max: 113.5, Diff: 0.0, Sum: 453.8]
[GC Worker End (ms): Min: 83383871.1, Avg: 83383871.1, Max: 83383871.1, Diff: 0.0]
[Code Root Fixup: 0.1 ms]
[Code Root Purge: 0.0 ms]
[String Dedup Fixup: 2.2 ms, GC Workers: 4]
[Queue Fixup (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Table Fixup (ms): Min: 2.0, Avg: 2.1, Max: 2.1, Diff: 0.1, Sum: 8.3]
[Clear CT: 0.1 ms]
[Other: 9.5 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 8.8 ms]
[Ref Enq: 0.1 ms]
[Redirty Cards: 0.3 ms]
[Humongous Reclaim: 0.0 ms]
[Free CSet: 0.1 ms]
[Eden: 215.0M(215.0M)->0.0B(215.0M) Survivors: 7168.0K->7168.0K Heap: 451.5M(512.0M)->236.6M(512.0M)]
[Times: user=0.08 sys=0.02, real=0.13 secs]
2015-05-31T18:25:25.129+0200: 83383.883: [GC concurrent-root-region-scan-start]
2015-05-31T18:25:25.129+0200: 83383.883: [GC concurrent-string-deduplication, 160.0B->0.0B(160.0B), avg 48.3%, 0.0000070 secs]
[Last Exec: 0.0000070 secs, Idle: 23.1834927 secs, Blocked: 0/0.0000000 secs]
[Inspected: 3]
[Skipped: 0( 0.0%)]
[Hashed: 3(100.0%)]
[Known: 0( 0.0%)]
[New: 3(100.0%) 160.0B]
[Deduplicated: 3(100.0%) 160.0B(100.0%)]
[Young: 3(100.0%) 160.0B(100.0%)]
[Old: 0( 0.0%) 0.0B( 0.0%)]
[Total Exec: 2868/0.1946124 secs, Idle: 2868/83382.9701762 secs, Blocked: 13/0.0032760 secs]
[Inspected: 304493]
[Skipped: 0( 0.0%)]
[Hashed: 163708( 53.8%)]
[Known: 44808( 14.7%)]
[New: 259685( 85.3%) 21.9M]
[Deduplicated: 160467( 61.8%) 10.6M( 48.3%)]
[Young: 83546( 52.1%) 6270.6K( 57.8%)]
[Old: 76921( 47.9%) 4571.3K( 42.2%)]
[Table]
[Memory Usage: 4291.8K]
[Size: 131072, Min: 1024, Max: 16777216]
[Entries: 133319, Load: 101.7%, Cached: 6107, Added: 142389, Removed: 9070]
[Resize Count: 7, Shrink Threshold: 87381(66.7%), Grow Threshold: 262144(200.0%)]
[Rehash Count: 0, Rehash Threshold: 120, Hash Seed: 0x0]
[Age Threshold: 3]
[Queue]
[Dropped: 0]
2015-05-31T18:25:25.145+0200: 83383.897: [GC concurrent-root-region-scan-end, 0.0140467 secs]
2015-05-31T18:25:25.145+0200: 83383.897: [GC concurrent-mark-start]
2015-05-31T18:25:35.563+0200: 83394.312: [GC concurrent-mark-end, 10.4145795 secs]
2015-05-31T18:25:35.563+0200: 83394.312: [GC remark 83394.312: [Finalize Marking, 0.0002939 secs] 83394.312: [GC ref-proc, 1.2128584 secs] 83395.525: [Unloading, 14.5180500 secs], 15.7320854 secs]
[Times: user=0.14 sys=0.22, real=15.73 secs]
2015-05-31T18:25:51.288+0200: 83410.045: [GC cleanup 334M->326M(512M), 0.2836092 secs]
[Times: user=0.00 sys=0.00, real=0.28 secs]
2015-05-31T18:25:51.570+0200: 83410.328: [GC concurrent-cleanup-start]
2015-05-31T18:25:51.570+0200: 83410.328: [GC concurrent-cleanup-end, 0.0000669 secs]
2015-05-31T18:26:03.732+0200: 83422.482: [GC pause (G1 Evacuation Pause) (young), 0.1031257 secs]
[Parallel Time: 91.6 ms, GC Workers: 4]
[GC Worker Start (ms): Min: 83422481.7, Avg: 83422481.7, Max: 83422481.8, Diff: 0.0]
[Ext Root Scanning (ms): Min: 1.3, Avg: 1.7, Max: 2.7, Diff: 1.4, Sum: 6.9]
[Update RS (ms): Min: 0.0, Avg: 22.7, Max: 89.8, Diff: 89.8, Sum: 90.8]
[Processed Buffers: Min: 0, Avg: 7.3, Max: 15, Diff: 15, Sum: 29]
[Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.2]
[Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Object Copy (ms): Min: 0.5, Avg: 2.4, Max: 3.4, Diff: 2.9, Sum: 9.5]
[Termination (ms): Min: 0.0, Avg: 64.7, Max: 86.3, Diff: 86.3, Sum: 258.9]
[GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
[GC Worker Total (ms): Min: 91.6, Avg: 91.6, Max: 91.6, Diff: 0.0, Sum: 366.3]
[GC Worker End (ms): Min: 83422573.3, Avg: 83422573.3, Max: 83422573.3, Diff: 0.0]
[Code Root Fixup: 0.1 ms]
[Code Root Purge: 0.0 ms]
[String Dedup Fixup: 2.1 ms, GC Workers: 4]
[Queue Fixup (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Table Fixup (ms): Min: 1.9, Avg: 1.9, Max: 1.9, Diff: 0.1, Sum: 7.7]
[Clear CT: 0.1 ms]
[Other: 9.3 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 8.8 ms]
[Ref Enq: 0.1 ms]
[Redirty Cards: 0.0 ms]
[Humongous Reclaim: 0.0 ms]
[Free CSet: 0.1 ms]
[Eden: 215.0M(215.0M)->0.0B(19.0M) Survivors: 7168.0K->6144.0K Heap: 443.6M(512.0M)->228.2M(512.0M)]
[Times: user=0.30 sys=0.01, real=0.10 secs]
2015-05-31T18:26:03.848+0200: 83422.597: [GC concurrent-string-deduplication, 160.0B->0.0B(160.0B), avg 48.3%, 0.0123951 secs]
[Last Exec: 0.0123951 secs, Idle: 38.7017788 secs, Blocked: 0/0.0000000 secs]
[Inspected: 3]
[Skipped: 0( 0.0%)]
[Hashed: 3(100.0%)]
[Known: 0( 0.0%)]
[New: 3(100.0%) 160.0B]
[Deduplicated: 3(100.0%) 160.0B(100.0%)]
[Young: 3(100.0%) 160.0B(100.0%)]
[Old: 0( 0.0%) 0.0B( 0.0%)]
[Total Exec: 2869/0.2070075 secs, Idle: 2869/83421.6719550 secs, Blocked: 13/0.0032760 secs]
[Inspected: 304496]
[Skipped: 0( 0.0%)]
[Hashed: 163711( 53.8%)]
[Known: 44808( 14.7%)]
[New: 259688( 85.3%) 21.9M]
[Deduplicated: 160470( 61.8%) 10.6M( 48.3%)]
[Young: 83549( 52.1%) 6270.8K( 57.8%)]
[Old: 76921( 47.9%) 4571.3K( 42.2%)]
[Table]
[Memory Usage: 2565.5K]
[Size: 65536, Min: 1024, Max: 16777216]
[Entries: 81061, Load: 123.7%, Cached: 6553, Added: 142396, Removed: 61335]
[Resize Count: 8, Shrink Threshold: 43690(66.7%), Grow Threshold: 131072(200.0%)]
[Rehash Count: 0, Rehash Threshold: 120, Hash Seed: 0x0]
[Age Threshold: 3]
[Queue]
[Dropped: 0]
2015-05-31T18:26:05.769+0200: 83424.518: [GC pause (G1 Evacuation Pause) (mixed), 0.2232916 secs]
[Parallel Time: 216.7 ms, GC Workers: 4]
[GC Worker Start (ms): Min: 83424518.3, Avg: 83424518.3, Max: 83424518.3, Diff: 0.0]
[Ext Root Scanning (ms): Min: 1.2, Avg: 1.6, Max: 2.6, Diff: 1.4, Sum: 6.5]
[Update RS (ms): Min: 0.0, Avg: 0.3, Max: 0.4, Diff: 0.4, Sum: 1.2]
[Processed Buffers: Min: 0, Avg: 4.3, Max: 7, Diff: 7, Sum: 17]
[Scan RS (ms): Min: 56.1, Avg: 102.3, Max: 144.4, Diff: 88.3, Sum: 409.2]
[Code Root Scanning (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 0.3]
[Object Copy (ms): Min: 50.4, Avg: 97.6, Max: 157.7, Diff: 107.2, Sum: 390.2]
[Termination (ms): Min: 0.0, Avg: 14.8, Max: 19.8, Diff: 19.8, Sum: 59.1]
[GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
[GC Worker Total (ms): Min: 216.6, Avg: 216.6, Max: 216.6, Diff: 0.0, Sum: 866.5]
[GC Worker End (ms): Min: 83424734.9, Avg: 83424734.9, Max: 83424734.9, Diff: 0.0]
[Code Root Fixup: 0.1 ms]
[Code Root Purge: 0.0 ms]
[String Dedup Fixup: 1.5 ms, GC Workers: 4]
[Queue Fixup (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Table Fixup (ms): Min: 1.4, Avg: 1.4, Max: 1.4, Diff: 0.0, Sum: 5.6]
[Clear CT: 0.2 ms]
[Other: 4.8 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 0.9 ms]
[Ref Enq: 0.0 ms]
[Redirty Cards: 0.2 ms]
[Humongous Reclaim: 0.0 ms]
[Free CSet: 0.2 ms]
[Eden: 19.0M(19.0M)->0.0B(21.0M) Survivors: 6144.0K->4096.0K Heap: 247.2M(512.0M)->175.2M(512.0M)]
[Times: user=0.09 sys=0.00, real=0.22 secs]
2015-05-31T18:26:05.992+0200: 83424.742: [GC concurrent-string-deduplication, 640.0B->152.0B(488.0B), avg 48.3%, 0.0000246 secs]
[Last Exec: 0.0000246 secs, Idle: 2.1442834 secs, Blocked: 0/0.0000000 secs]
[Inspected: 6]
[Skipped: 0( 0.0%)]
[Hashed: 5( 83.3%)]
[Known: 0( 0.0%)]
[New: 6(100.0%) 640.0B]
[Deduplicated: 5( 83.3%) 488.0B( 76.3%)]
[Young: 5(100.0%) 488.0B(100.0%)]
[Old: 0( 0.0%) 0.0B( 0.0%)]
[Total Exec: 2870/0.2070321 secs, Idle: 2870/83423.8162384 secs, Blocked: 13/0.0032760 secs]
[Inspected: 304502]
[Skipped: 0( 0.0%)]
[Hashed: 163716( 53.8%)]
[Known: 44808( 14.7%)]
[New: 259694( 85.3%) 21.9M]
[Deduplicated: 160475( 61.8%) 10.6M( 48.3%)]
[Young: 83554( 52.1%) 6271.2K( 57.8%)]
[Old: 76921( 47.9%) 4571.3K( 42.2%)]
[Table]
[Memory Usage: 2564.6K]
[Size: 65536, Min: 1024, Max: 16777216]
[Entries: 81026, Load: 123.6%, Cached: 6553, Added: 142397, Removed: 61371]
[Resize Count: 8, Shrink Threshold: 43690(66.7%), Grow Threshold: 131072(200.0%)]
[Rehash Count: 0, Rehash Threshold: 120, Hash Seed: 0x0]
[Age Threshold: 3]
[Queue]
[Dropped: 0]
2015-05-31T18:26:08.157+0200: 83426.906: [GC pause (G1 Evacuation Pause) (mixed), 0.6216666 secs]
[Parallel Time: 618.5 ms, GC Workers: 4]
[GC Worker Start (ms): Min: 83426906.5, Avg: 83426906.5, Max: 83426906.5, Diff: 0.0]
[Ext Root Scanning (ms): Min: 0.3, Avg: 8.0, Max: 15.7, Diff: 15.3, Sum: 31.9]
[Update RS (ms): Min: 0.0, Avg: 4.5, Max: 8.5, Diff: 8.5, Sum: 17.9]
[Processed Buffers: Min: 0, Avg: 7.0, Max: 18, Diff: 18, Sum: 28]
[Scan RS (ms): Min: 13.4, Avg: 28.4, Max: 65.2, Diff: 51.8, Sum: 113.7]
[Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.2]
[Object Copy (ms): Min: 532.6, Avg: 577.3, Max: 604.5, Diff: 71.9, Sum: 2309.1]
[Termination (ms): Min: 0.0, Avg: 0.2, Max: 0.3, Diff: 0.3, Sum: 0.7]
[GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
[GC Worker Total (ms): Min: 618.4, Avg: 618.4, Max: 618.4, Diff: 0.0, Sum: 2473.6]
[GC Worker End (ms): Min: 83427524.9, Avg: 83427524.9, Max: 83427524.9, Diff: 0.0]
[Code Root Fixup: 0.1 ms]
[Code Root Purge: 0.0 ms]
[String Dedup Fixup: 1.3 ms, GC Workers: 4]
[Queue Fixup (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
[Table Fixup (ms): Min: 1.2, Avg: 1.2, Max: 1.3, Diff: 0.1, Sum: 4.9]
[Clear CT: 0.1 ms]
[Other: 1.6 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 1.0 ms]
[Ref Enq: 0.0 ms]
[Redirty Cards: 0.0 ms]
[Humongous Reclaim: 0.0 ms]
[Free CSet: 0.2 ms]
[Eden: 21.0M(21.0M)->0.0B(21.0M) Survivors: 4096.0K->4096.0K Heap: 196.2M(512.0M)->129.4M(512.0M)]
[Times: user=0.08 sys=0.02, real=0.62 secs]
每秒有很多页面，每秒有很多页面输入，还有页面错误。这正常吗？我在哪里可以设置为仅为JVM监控每秒页面数和每秒页面输入数（我只发现页面错误）？我猜你找错了方向-我怀疑垃圾收集不是你的问题 您只运行一个512 MiB堆-对我来说，对一个大小为1或2秒的堆进行长时间暂停。对于巨大的（32 GiB）堆，以毫秒为单位的主要暂停是可能的 我认为问题实际上在于您的服务器——或者您提到的其他应用程序正在使用足够的内存将Java进程（大约比堆大50%）推入交换/虚拟内存——或者您正在虚拟化环境中运行应用程序（可能存在内存过度使用/内存平衡问题） 作为一个非常粗糙的指标，任何GC算法都应该能够每秒搅动100个MiB的堆-因此，如果您看到比这更糟糕的情况，请从别处寻找问题的原因 在这种情况下，我相信GC是症状，而不是问题 [次数：用户=0.14系统=0.22，实际=15.73秒] 这意味着它花费的挂机时间比实际的CPU时间多得多。您尝试过的所有GC都是多线程的，纯CPU限制的，这意味着它们通常应该比挂机时间消耗更多的CPU时间 有两个可能的原因可以改变这种情况
- 资源不足，或者堆的一部分被换掉，或者其他进程正在占用CPU。正如@Mikaveli所建议的，使用操作系统监视工具获取更多信息
- 有些东西阻止VM在几秒钟内到达安全点。您可以使用
-XX:+PrintSafepointStatistics-XX:printsafepointstatisticscont=1检查这一点
-XX:-ClassUnloadingWithConcurrentMark-XX:+TraceClassUnloading至于CMS与G1：这可能与您的问题无关。您正在将最大堆大小（xmx）设置为初始大小（xms）（512）。为什么不增加它呢？.i7有足够的内核。所以CMS或g1gc应该可以正常工作（默认情况下可以选择）。我不想使用太多内存，因为还有其他应用程序（不是glassfish）在这台电脑上运行。我认为512m的堆大小对于这个应用程序来说已经足够了。如果我将堆大小增加到1024m，主GC和次GC将很少发生，但暂停时间会相同，甚至更高，或者我的想法不对？随着堆的增加，暂停时间会更高，但GC的频率会更低。我认为这是一个安全的赌注。你不应该这样做ry增加堆并检查结果是的，但我在暂停时间而不是频率方面有问题-如果暂停时间更短（<5秒），我不在乎是否有更多GC