Java 1.8安全点超时 [英] Java 1.8 safepoint timeout
问题描述
我似乎遇到了这样一种情况:JVM无限期地陷入困境，试图在几个小时后到达安全点.但是，如果我使用-F选项执行jstack，似乎可以避免等待并继续执行.
I seem to be running into a scenario where the JVM is stuck indefinitely in trying to get to a safe point after a few hours. However, if I do a jstack with -F option it seems to get out of that wait and continues with the execution.
jdk1.8.0_45/bin/jstack -F 39924> a.out
jdk1.8.0_45/bin/jstack -F 39924 >a.out
我在Centos上使用jdk1.8.0_45
I am using jdk1.8.0_45 on Centos
我的问题是:
i)当从jstack发送中断时，JVM似乎可以脱离安全点无限期等待.没有jstack怎么不会出来.是否可以使用一些jvm选项来避免无限期等待.
i) It seems that the JVM can come out of that safepoint indefinite wait when sent an interrupt from jstack. How come it doesnt come out without jstack. Is there some jvm option I can use to avoid that indefinite wait.
ii)是否可以对引起问题的线程进行更明确的线程转储.安全点日志的输出似乎不准确.
ii) Can I get a more definite thread dump of the the thread that's causing the issue. The output from the safepoint log seems imprecise.
我正在使用的选项是:.
The options I am using are:.
-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，这就是我从安全点日志中看到的内容
After the jstack interrupt this is what I see from the safepoint log
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
推荐答案
由于您可以通过中断VM来解决问题，并且您使用的是CentOS，因此该问题使我想起了
Since you are able to remedy the problem by interrupting the VM and you're on CentOS the problem reminds me of this kernel bug.
该线程列出了以下受影响的版本(假定标准内核):
The thread lists the following affected versions (assuming standard kernels):
- RHEL 6(以及CentOS 6和SL 6):6.0-6.5很好. 6.6是BAD. 6.6.z 很好.
- RHEL 7(以及CentOS 7和SL 7):7.1是错误的.截至昨天. 似乎还没有7.x修复程序.
- RHEL 5(和CentOS 5，以及 SL 5):所有版本都不错(包括5.11).
- 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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