序
本文主要研究一下java9 gc log參數(shù)的遷移逮诲。
統(tǒng)一JVM及GC的Logging
java9引進了一個統(tǒng)一的日志框架瓢喉，對gc log的輸出進行了統(tǒng)一的配置。
相關(guān)JEP(JDK Enhancement Proposal)
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皂冰，其他的如下：
add贿讹，age吠裆，alloc伐谈，annotation，aot试疙，arguments诵棵，attach，barrier祝旷，biasedlocking履澳，blocks，bot缓屠，breakpoint，bytecode护侮，census敌完，class，classhisto羊初，cleanup滨溉，compaction，comparator长赞，constraints晦攒，constantpool，coops得哆，cpu脯颜，cset，data贩据，defaultmethods栋操，dump，ergo饱亮，event矾芙，exceptions，exit近上，fingerprint剔宪，freelist，gc，hashtables葱绒，heap感帅，humongous，ihop哈街，iklass留瞳，init，itables骚秦，jfr她倘，jni，jvmti作箍，liveness硬梁，load，loader胞得，logging荧止，mark，marking阶剑，metadata跃巡，metaspace，method牧愁，mmu素邪，modules，monitorinflation猪半，monitormismatch兔朦，nmethod，normalize磨确，objecttagging沽甥，obsolete，oopmap乏奥，os摆舟，pagesize，parser邓了，patch盏檐，path，phases驶悟，plab胡野，preorder，promotion痕鳍，protectiondomain硫豆，purge龙巨，redefine，ref熊响，refine旨别，region，remset汗茄，resolve秸弛，safepoint，scavenge洪碳，scrub递览，setting，stackmap瞳腌，stacktrace绞铃，stackwalk，start嫂侍，startuptime儿捧，state，stats挑宠，stringdedup菲盾，stringtable，subclass各淀，survivor懒鉴，sweep，system揪阿，task疗我，thread咆畏，time南捂，timer，tlab旧找，unload溺健，update，verification钮蛛，verify鞭缭，vmoperation，vtables魏颓，workgang
level
主要分off岭辣，trace，debug甸饱，info沦童，warning仑濒，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的話偷遗，可以使用%p變量表示當前jvm的pid墩瞳，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
不指定的話氏豌，默認是uptime, level, and tags這三個喉酌。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泵喘，rotate文件數(shù)為5泪电，每個文件1M，文件名為gctrace.txt涣旨，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. |
小結(jié)
java9把gc log的配置統(tǒng)一到了Xlog中歪架，可以按照官方給出的新舊參數(shù)映射表進行遷移。
