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一直以來，發現有某些人完全不尊重我的勞動成果，隨意轉載，提醒一下那些人小心哪天惹上官司。
IBM Pattern Modeling and Analysis Tool for Java Garbage Collector(簡稱GA)，大名鼎鼎的IBM用來分析JDK GC日志的工具，2008年8月23日，更新至2.6版，增加了對Java 6 GC日志的分析。
我想這也是為了配合Websphere Application Server 7.0的測試版發布，在我之前的一篇文章《
WebSphere Application Server 7.0 初體驗》中曾經提到，GCViewer這個工具目前還無法查看其GC的日志，現在不用擔心這個問題了，用GA2.6來看吧。
來看看官方的簡介：
What?is?Pattern?Modeling?and?Analysis?Tool?for?IBM?Java?Garbage?Collector?
Pattern?Modeling?and?Analysis?Tool?for?IBM??Java??Garbage?Collector?(PMAT)?parses?verbose?GC?trace,?analyzes?Java?heap?usage,?and?recommends?key?configurations?based?on?pattern?modeling?of?Java?heap?usage.?
When?the?JVM?(Java?virtual?machine)?cannot?allocate?an?object?from?the?current?heap?because?of?lack?of?space,?a?memory?allocation?fault?occurs,?and?the?Garbage?Collector?is?invoked.?The?first?task?of?the?Garbage?Collector?is?to?collect?all?the?garbage?that?is?in?the?heap.?This?process?starts?when?any?thread?calls?the?Garbage?Collector?either?indirectly?as?a?result?of?allocation?failure?or?directly?by?a?specific?call?to?System.gc().?The?first?step?is?to?get?all?the?locks?needed?by?the?garbage?collection?process.?This?step?ensures?that?other?threads?are?not?suspended?while?they?are?holding?critical?locks.?All?other?threads?are?then?suspended.?Garbage?collection?can?then?begin.?It?occurs?in?three?phases:?Mark,?Sweep,?and?Compaction?(optional).?
Verbose?GC?is?a?command-line?option?that?one?can?supply?to?the?JVM?at?start-up?time.?The?format?is:?-verbose:gc?or?-verbosegc.?This?option?switches?on?a?substantial?trace?of?every?garbage?collection?cycle.?The?format?for?the?generated?information?is?not?designed?and?therefore?varies?among?various?platforms?and?releases.?
This?trace?should?allow?one?to?see?the?gross?heap?usage?in?every?garbage?collection?cycle.?For?example,?one?could?monitor?the?output?to?see?the?changes?in?the?free?heap?space?and?the?total?heap?space.?This?information?can?be?used?to?determine?whether?garbage?collections?are?taking?too?long?to?run;?whether?too?many?garbage?collections?are?occurring;?and?whether?the?JVM?crashed?during?garbage?collection.?
更多訊息，可以參考其官方網站：
http://alphaworks.ibm.com/tech/pmatWAS的GC日志的獲得方法，可以參見我的另一篇文章《
WebSphere Application Server 7.0 初體驗》，當然也可以看WAS的文檔或此軟件的文檔。
下圖是我試用WAS7.0產生的GC Log的Chart View：
有興趣的朋友們可以試試看。
posted on 2008-09-01 00:11
Robin's Programming World 閱讀(3252)
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