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統一JVM及GC的Logging
java9引進了一個統一的日志框架，把gc相關的log輸出及配置也給納入進來了。
相關JEP(JDK Enhancement Proposal)
Xlog語法
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-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：
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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
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- 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變量表示當前jvm的pid，用%t表示jvm的啟動時間戳。比如
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-Xlog:gc:demoapp-gc-%p-%t.log |
輸出的文件名如下：
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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，默認是uptime, level, and tags這三個。比如
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[3.080s][info][gc,cpu ] GC(5) User=0.03s Sys=0.00s Real=0.01s |
實例
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-Xlog:gc=trace:file=gctrace.txt:uptimemillis,pid:filecount=5,filesize=1024 |
tag為gc，levle為trace，rotate文件數為5，每個文件1M，文件名為gctrace.txt，decrotators為uptimemillis和pid
輸出實例
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[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相關參數遷移
| 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
java9把gc log的選型及輸出也給統一到了Xlog中，可以按照官方給出的遷移表進行遷移。
原文鏈接：https://segmentfault.com/a/1190000013475524
