java9中g(shù)c log參數(shù)遷移

更新時間：2018年03月02日 08:44:20 作者：codecraft

本篇文章給大家詳細(xì)講述了java9中g(shù)c log參數(shù)遷移的相關(guān)知識點，對此有需要的朋友可以參考學(xué)習(xí)下。

序

本文主要研究一下java9 gc log參數(shù)的遷移。

統(tǒng)一JVM及GC的Logging

java9引進(jìn)了一個統(tǒng)一的日志框架，把gc相關(guān)的log輸出及配置也給納入進(jìn)來了。

相關(guān)JEP(JDK Enhancement Proposal)

JEP 158: Unified JVM Logging
JEP 264: Platform Logging API and Service
JEP 271: Unified GC Logging

Xlog語法

-Xlog[:option]
  option     := [<what>][:[<output>][:[<decorators>][:<output-options>]]]
            'help'
            'disable'
  what      := <selector>[,...]
  selector    := <tag-set>[*][=<level>]
  tag-set    := <tag>[+...]
            'all'
  tag      := name of tag
  level     := trace
            debug
            info
            warning
            error
  output     := 'stderr'
            'stdout'
            [file=]<filename>
  decorators   := <decorator>[,...]
            'none'
  decorator   := time
            uptime
            timemillis
            uptimemillis
            timenanos
            uptimenanos
            pid
            tid
            level
            tags
  output-options := <output_option>[,...]
  output-option := filecount=<file count>
            filesize=<file size in kb>
            parameter=value

what

主要是配置tag及l(fā)evel

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(`Sends output to stdout`)
- stderr(`Sends output to stderr`)
- file=filename(`Sends output to text file(s)`)

有如上三種，其中指定file的話，可以使用%p變量表示當(dāng)前jvm的pid，用%t表示jvm的啟動時間戳。比如

-Xlog:gc:demoapp-gc-%p-%t.log

輸出的文件名如下：

demoapp-gc-1678-2018-03-01_21-44-18.log

decorators

time -- Current time and date in ISO-8601 format
uptime -- Time since the start of the JVM in seconds and milliseconds (e.g., 6.567s)
timemillis -- The same value as generated by System.currentTimeMillis()
uptimemillis -- Milliseconds since the JVM started
timenanos -- The same value as generated by System.nanoTime()
uptimenanos -- Nanoseconds since the JVM started
pid -- The process identifier
tid -- The thread identifier
level -- The level associated with the log message
tags -- The tag-set associated with the log message

不指定的話，默認(rèn)是uptime, level, and tags這三個。比如

[3.080s][info][gc,cpu ] GC(5) User=0.03s Sys=0.00s Real=0.01s

實例

-Xlog:gc=trace:file=gctrace.txt:uptimemillis,pid:filecount=5,filesize=1024

tag為gc，levle為trace，rotate文件數(shù)為5，每個文件1M，文件名為gctrace.txt，decrotators為uptimemillis和pid

輸出實例

[1110ms][1867] GC(2) Pause Remark 17M->17M(256M) 2.024ms
[1110ms][1867] GC(2) Finalize Live Data 0.000ms
[1110ms][1867] GC(2) Pause Cleanup 17M->17M(256M) 0.177ms
[1112ms][1867] GC(2) Concurrent Cycle 7.470ms
[2951ms][1867] GC(3) Pause Initial Mark (Metadata GC Threshold) 149M->30M(256M) 27.175ms
[2951ms][1867] GC(4) Concurrent Cycle
[2972ms][1867] GC(4) Pause Remark 32M->32M(256M) 5.132ms
[2974ms][1867] GC(4) Finalize Live Data 0.000ms
[2974ms][1867] GC(4) Pause Cleanup 32M->32M(256M) 0.214ms
[2976ms][1867] GC(4) Concurrent Cycle 25.422ms

遷移

舊版GC相關(guān)參數(shù)遷移

Legacy Garbage Collection (GC) Flag	Xlog Configuration	Comment
G1PrintHeapRegions	-Xlog:gc+region=trace	Not Applicable
GCLogFileSize	No configuration available	Log rotation is handled by the framework.
NumberOfGCLogFiles	Not Applicable	Log rotation is handled by the framework.
PrintAdaptiveSizePolicy	-Xlog:ergo*=level	Use a level of debug for most of the information, or a level of trace for all of what was logged for PrintAdaptiveSizePolicy.
PrintGC	-Xlog:gc	Not Applicable
PrintGCApplicationConcurrentTime	-Xlog:safepoint	Note that PrintGCApplicationConcurrentTime and PrintGCApplicationStoppedTime are logged on the same tag and aren't separated in the new logging.
PrintGCApplicationStoppedTime	-Xlog:safepoint	Note that PrintGCApplicationConcurrentTime and PrintGCApplicationStoppedTime are logged on the same tag and not separated in the new logging.
PrintGCCause	Not Applicable	GC cause is now always logged.
PrintGCDateStamps	Not Applicable	Date stamps are logged by the framework.
PrintGCDetails	-Xlog:gc*	Not Applicable
PrintGCID	Not Applicable	GC ID is now always logged.
PrintGCTaskTimeStamps	-Xlog:task*=debug	Not Applicable
PrintGCTimeStamps	Not Applicable	Time stamps are logged by the framework.
PrintHeapAtGC	-Xlog:gc+heap=trace	Not Applicable
PrintReferenceGC	-Xlog:ref*=debug	Note that in the old logging, PrintReferenceGC had an effect only if PrintGCDetails was also enabled.
PrintStringDeduplicationStatistics	-Xlog:stringdedup*=debug	Not Applicable
PrintTenuringDistribution	-Xlog:age*=level	Use a level of debug for the most relevant information, or a level of trace for all of what was logged for PrintTenuringDistribution.
UseGCLogFileRotation	Not Applicable	What was logged for PrintTenuringDistribution.

舊版運行時參數(shù)遷移

Legacy Runtime Flag	Xlog Configuration	Comment
TraceExceptions	-Xlog:exceptions=info	Not Applicable
TraceClassLoading	-Xlog:class+load=level	Use level=info for regular information, or level=debug for additional information. In Unified Logging syntax, -verbose:class equals -Xlog:class+load=info,class+unload=info.
TraceClassLoadingPreorder	-Xlog:class+preorder=debug	Not Applicable
TraceClassUnloading	-Xlog:class+unload=level	Use level=info for regular information, or level=trace for additional information. In Unified Logging syntax, -verbose:class equals -Xlog:class+load=info,class+unload=info.
VerboseVerification	-Xlog:verification=info	Not Applicable
TraceClassPaths	-Xlog:class+path=info	Not Applicable
TraceClassResolution	-Xlog:class+resolve=debug	Not Applicable
TraceClassInitialization	-Xlog:class+init=info	Not Applicable
TraceLoaderConstraints	-Xlog:class+loader+constraints=info	Not Applicable
TraceClassLoaderData	-Xlog:class+loader+data=level	Use level=debug for regular information or level=trace for additional information.
TraceSafepointCleanupTime	-Xlog:safepoint+cleanup=info	Not Applicable
TraceSafepoint	-Xlog:safepoint=debug	Not Applicable
TraceMonitorInflation	-Xlog:monitorinflation=debug	Not Applicable
TraceBiasedLocking	-Xlog:biasedlocking=level	Use level=info for regular information, or level=trace for additional information.
TraceRedefineClasses	-Xlog:redefine+class*=level	level=info, =debug, and =trace provide increasing amounts of information.