Java 1.8安全点超时

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我似乎遇到了一个场景,JVM在几个小时后试图达到一个安全点时无限期地陷入困境.但是,如果我使用-F选项执行jstack,它似乎就会退出等待并继续执行.

jdk1.8.0_45 / bin / jstack -F 39924> a.out

我在Centos上使用jdk1.8.0_45

我的问题是：

i)当从jstack发送中断时,似乎JVM可以从安全点无限期等待.如果没有jstack它怎么会出来.是否有一些jvm选项我可以用来避免无限期等待.

ii)我是否可以获得导致问题的线程更明确的线程转储.安全点日志的输出似乎不精确.

我使用的选项是：

-server
-XX:+AggressiveOpts
-XX:+UseG1GC
-XX:+UnlockExperimentalVMOptions
-XX:G1MixedGCLiveThresholdPercent=85
-XX:InitiatingHeapOccupancyPercent=30
-XX:G1HeapWastePercent=5 
-XX:MaxGCPauseMillis=1000
-XX:G1HeapRegionSize=4M
-XX:+PrintGC
-XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-XX:+PrintGCDateStamps
-XX:+UnlockExperimentalVMOptions
-XX:G1LogLevel=finest
-Xmx6000m
-Xdebug
-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=999
-XX:+SafepointTimeout
-XX:+UnlockDiagnosticVMOptions
-XX:SafepointTimeoutDelay=20000
-XX:+PrintSafepointStatistics
-XX:PrintSafepointStatisticsCount=1 

安全点日志

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17771.115: G1IncCollectionPause             [     170          0              0    ]      [     0     0     0     0     8    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17771.125: RevokeBias                       [     170          1              2    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17771.127: RevokeBias                       [     170          1              1    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17771.131: RevokeBias                       [     170          1              2    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17771.955: RevokeBias                       [     169          0              2    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17772.160: BulkRevokeBias                   [     171          0              2    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17772.352: RevokeBias                       [     170          1              3    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17773.596: RevokeBias                       [     169          0              1    ]      [     0     0     0     0     0    ]  0

 # SafepointSynchronize::begin: Timeout detected:
 # SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.
 # SafepointSynchronize::begin: Threads which did not reach the safepoint:
 # "Thread-14" #115 prio=5 os_prio=0 tid=0x00007f20c8029000 nid=0x9cd0 runnable [0x0000000000000000]    java.lang.Thread.State: RUNNABLE
 # SafepointSynchronize::begin: (End of list)

在jstack中断之后,这是我从安全点日志中看到的

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
17779.826: G1IncCollectionPause             [     169          1              1    ]      [3315603     03315603     0     8    ]  1

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
21095.439: RevokeBias                       [     169          2             13    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
21095.439: RevokeBias                       [     169          1              2    ]      [     0     0     0     0     0    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
21095.441: RevokeBias                       [     184          3              4    ]      [     0     0     3     0     1    ]  0

vmop                    [threads: total initially_running wait_to_block]    [time: spin block sync cleanup vmop] page_trap_count
21095.447: RevokeBias                       [     190          0              2    ]      [     0     0     4     0     2    ]  0

解决方法:

由于您可以通过中断VM来解决问题,而您在CentOS上的问题让我想起了this kernel bug.

该线程列出了以下受影响的版本(假设标准内核)：

• RHEL 6 (and CentOS 6, and SL 6): 6.0-6.5 are good. 6.6 is BAD. 6.6.z
  is good.
• RHEL 7 (and CentOS 7, and SL 7): 7.1 is BAD. As of yesterday.
  there does not yet appear to be a 7.x fix.
• RHEL 5 (and CentOS 5, and
  SL 5): All versions are good (including 5.11).

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