java9中gc log参数迁移
序
本文主要研究一下java9gclog参数的迁移。
统一JVM及GC的Logging
java9引进了一个统一的日志框架，把gc相关的log输出及配置也给纳入进来了。
相关JEP(JDKEnhancementProposal)
- JEP158:UnifiedJVMLogging
- JEP264:PlatformLoggingAPIandService
- JEP271:UnifiedGCLogging
Xlog语法
-Xlog[:option] option:=[][:[
what
主要是配置tag及level
tag
其中all代表所有的tag，其他的如下：
add，age，alloc，annotation，aot，arguments，attach，barrier，biasedlocking，blocks，bot，breakpoint，bytecode，census，class，classhisto，cleanup，compaction，comparator，constraints，constantpool，coops，cpu，cset，data，defaultmethods，dump，ergo，event，exceptions，exit，fingerprint，freelist，gc，hashtables，heap，humongous，ihop，iklass，init，itables，jfr，jni，jvmti，liveness，load，loader，logging，mark，marking，metadata，metaspace，method，mmu，modules，monitorinflation，monitormismatch，nmethod，normalize，objecttagging，obsolete，oopmap，os，pagesize，parser，patch，path，phases，plab，preorder，promotion，protectiondomain，purge，redefine，ref，refine，region，remset，resolve，safepoint，scavenge，scrub，setting，stackmap，stacktrace，stackwalk，start，startuptime，state，stats，stringdedup，stringtable，subclass，survivor，sweep，system，task，thread，time，timer，tlab，unload，update，verification，verify，vmoperation，vtables，workgang
level
主要分off，trace，debug，info，warning，error
output
-stdout(`Sendsoutputtostdout`) -stderr(`Sendsoutputtostderr`) -file=filename(`Sendsoutputtotextfile(s)`)
有如上三种，其中指定file的话，可以使用%p变量表示当前jvm的pid，用%t表示jvm的启动时间戳。比如
-Xlog:gc:demoapp-gc-%p-%t.log
输出的文件名如下：
demoapp-gc-1678-2018-03-01_21-44-18.log
decorators
- time--CurrenttimeanddateinISO-8601format
- uptime--TimesincethestartoftheJVMinsecondsandmilliseconds(e.g.,6.567s)
- timemillis--ThesamevalueasgeneratedbySystem.currentTimeMillis()
- uptimemillis--MillisecondssincetheJVMstarted
- timenanos--ThesamevalueasgeneratedbySystem.nanoTime()
- uptimenanos--NanosecondssincetheJVMstarted
- pid--Theprocessidentifier
- tid--Thethreadidentifier
- level--Thelevelassociatedwiththelogmessage
- tags--Thetag-setassociatedwiththelogmessage
不指定的话，默认是uptime,level,andtags这三个。比如
[3.080s][info][gc,cpu]GC(5)User=0.03sSys=0.00sReal=0.01s
实例
-Xlog:gc=trace:file=gctrace.txt:uptimemillis,pid:filecount=5,filesize=1024
tag为gc，levle为trace，rotate文件数为5，每个文件1M，文件名为gctrace.txt，decrotators为uptimemillis和pid
输出实例
[1110ms][1867]GC(2)PauseRemark17M->17M(256M)2.024ms [1110ms][1867]GC(2)FinalizeLiveData0.000ms [1110ms][1867]GC(2)PauseCleanup17M->17M(256M)0.177ms [1112ms][1867]GC(2)ConcurrentCycle7.470ms [2951ms][1867]GC(3)PauseInitialMark(MetadataGCThreshold)149M->30M(256M)27.175ms [2951ms][1867]GC(4)ConcurrentCycle [2972ms][1867]GC(4)PauseRemark32M->32M(256M)5.132ms [2974ms][1867]GC(4)FinalizeLiveData0.000ms [2974ms][1867]GC(4)PauseCleanup32M->32M(256M)0.214ms [2976ms][1867]GC(4)ConcurrentCycle25.422ms
迁移
旧版GC相关参数迁移
| LegacyGarbageCollection(GC)Flag | XlogConfiguration | Comment |
|---|---|---|
| G1PrintHeapRegions | -Xlog:gc+region=trace | NotApplicable |
| GCLogFileSize | Noconfigurationavailable | Logrotationishandledbytheframework. |
| NumberOfGCLogFiles | NotApplicable | Logrotationishandledbytheframework. |
| PrintAdaptiveSizePolicy | -Xlog:ergo*=level | Usealevelofdebugformostoftheinformation,oraleveloftraceforallofwhatwasloggedforPrintAdaptiveSizePolicy. |
| PrintGC | -Xlog:gc | NotApplicable |
| PrintGCApplicationConcurrentTime | -Xlog:safepoint | NotethatPrintGCApplicationConcurrentTimeandPrintGCApplicationStoppedTimeareloggedonthesametagandaren'tseparatedinthenewlogging. |
| PrintGCApplicationStoppedTime | -Xlog:safepoint | NotethatPrintGCApplicationConcurrentTimeandPrintGCApplicationStoppedTimeareloggedonthesametagandnotseparatedinthenewlogging. |
| PrintGCCause | NotApplicable | GCcauseisnowalwayslogged. |
| PrintGCDateStamps | NotApplicable | Datestampsareloggedbytheframework. |
| PrintGCDetails | -Xlog:gc* | NotApplicable |
| PrintGCID | NotApplicable | GCIDisnowalwayslogged. |
| PrintGCTaskTimeStamps | -Xlog:task*=debug | NotApplicable |
| PrintGCTimeStamps | NotApplicable | Timestampsareloggedbytheframework. |
| PrintHeapAtGC | -Xlog:gc+heap=trace | NotApplicable |
| PrintReferenceGC | -Xlog:ref*=debug | Notethatintheoldlogging,PrintReferenceGChadaneffectonlyifPrintGCDetailswasalsoenabled. |
| PrintStringDeduplicationStatistics | -Xlog:stringdedup*=debug | NotApplicable |
| PrintTenuringDistribution | -Xlog:age*=level | Usealevelofdebugforthemostrelevantinformation,oraleveloftraceforallofwhatwasloggedforPrintTenuringDistribution. |
| UseGCLogFileRotation | NotApplicable | WhatwasloggedforPrintTenuringDistribution. |
旧版运行时参数迁移
| LegacyRuntimeFlag | XlogConfiguration | Comment |
|---|---|---|
| TraceExceptions | -Xlog:exceptions=info | NotApplicable |
| TraceClassLoading | -Xlog:class+load=level | Uselevel=infoforregularinformation,orlevel=debugforadditionalinformation.InUnifiedLoggingsyntax,-verbose:classequals-Xlog:class+load=info,class+unload=info. |
| TraceClassLoadingPreorder | -Xlog:class+preorder=debug | NotApplicable |
| TraceClassUnloading | -Xlog:class+unload=level | Uselevel=infoforregularinformation,orlevel=traceforadditionalinformation.InUnifiedLoggingsyntax,-verbose:classequals-Xlog:class+load=info,class+unload=info. |
| VerboseVerification | -Xlog:verification=info | NotApplicable |
| TraceClassPaths | -Xlog:class+path=info | NotApplicable |
| TraceClassResolution | -Xlog:class+resolve=debug | NotApplicable |
| TraceClassInitialization | -Xlog:class+init=info | NotApplicable |
| TraceLoaderConstraints | -Xlog:class+loader+constraints=info | NotApplicable |
| TraceClassLoaderData | -Xlog:class+loader+data=level | Uselevel=debugforregularinformationorlevel=traceforadditionalinformation. |
| TraceSafepointCleanupTime | -Xlog:safepoint+cleanup=info | NotApplicable |
| TraceSafepoint | -Xlog:safepoint=debug | NotApplicable |
| TraceMonitorInflation | -Xlog:monitorinflation=debug | NotApplicable |
| TraceBiasedLocking | -Xlog:biasedlocking=level | Uselevel=infoforregularinformation,orlevel=traceforadditionalinformation. |
| TraceRedefineClasses | -Xlog:redefine+class*=level | level=info,=debug,and=traceprovideincreasingamountsofinformation. |
小结
java9把gclog的选型及输出也给统一到了Xlog中，可以按照官方给出的迁移表进行迁移。
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