java9 gc log参数迁移

最新推荐文章于 2025-06-30 02:49:33 发布

转载最新推荐文章于 2025-06-30 02:49:33 发布 · 706 阅读

文章标签：

#JVM #Java #gc #参数

JVM 专栏收录该内容

1 篇文章

订阅专栏

本文详细介绍了Java9引入的统一JVM及GC日志框架，解释了如何使用-Xlog参数进行GC日志配置，包括tag、level、output等选项，并提供了从旧版GC参数到新版Xlog配置的迁移指南。

原文链接：https://segmentfault.com/a/1190000013475524

序

本文主要研究一下java9 gc log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，对gc log的输出进行了统一的配置。

相关JEP(JDK Enhancement Proposal)

Xlog语法

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

不指定的话，默认是uptime, level, and tags这三个。比如

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

迁移

旧版GC相关参数迁移

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.

旧版运行时参数迁移

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.

小结

java9把gc log的配置统一到了Xlog中，可以按照官方给出的新旧参数映射表进行迁移。