小型JIT编译器之最佳化技术评估.ppt

小型JIT編譯器之最佳化技術評估,指導教授:單智君老師指導學長:喬偉豪學長組員:鍾懿軒，蔣季融，李國丞,Outline,觀察-鍾懿軒動機-鍾懿軒目標-鍾懿軒初步設計-李國丞修改過的設計-蔣季融未來進度-蔣季融,觀察,Java是用stack運算。因為底層機器是register-based非stack-based，用interpreter執行，performance不佳。加入JIT將bytecode轉換為register-based的指令，可以增進performance。若於JIT中加入一些機制，增進其效能，則可進一步增進javaperformance。,動機,加入的機制若能產生IR，使JITcompiler後端處理更方便。就有可能增進JIT的速度。folding機制:讀入bytecode產生register-based的IR，簡便後段處理。因此決定於JIT中加入folding機制。,目標,將folding機制加入JIT中，以最少的overhead，fold最多的pattern，達到增加performance的目的。,初步設計,架構圖Bytecode分類Pattern統計遇到的問題,舊架構圖,舊folding架構圖,Bytecode分類,1.定義:參考kimspaper(AdvancedPOCModel-BasedJavaInstructionFoldingMechanism)P:非operation含有push。Op:operation含有push不含pop。Oc:operation含有pop不含push。C:非operation含有pop。On:不含pushpop,無法分類者。,Bytecode分類(續),參考學長的paper(stackoperationsfoldinginjavaprocessors)P:transferingdatafromConstantRegisterorLocalVariabletotheoperandstack。O:getsdatafromtheoperandstackandthenperformsdifferenttasksOe:ALUtypeoperatorthatwritestheresultbacktotheoperandstack。Ob:Branchtypeoperator。Oc:Complextypeoperatorincludingarrayaccess,constantpoolaccess。Ot:unableorhardtojointhefoldingoperation。C:consumesdatafromtheoperandstack,andstoresdatabackintothelocalvariable。,Bytecode分類(續),2.統計bytecodepush/pop數:檢視kvmsourcecode(bytecodes.c):查看每道bytecode的執行碼中有多少push,pop的動作。檢視jvmspec(chapter6)每道bytecode都已規定好stack情況，可直接紀錄。,AnalyzepatternspossibilityinJavaclassfile,GetinformationfromJavaclassfileDoitourself(inC+)BCELlibraryforJava(/bcel),Possibilityofpatterns,(1)KIM所統計出的Patterns及出現百分比(2)自行統計”EmbeddedCaffeineMark”的結果,Problems,ClassificationcansavetimeofstringmatchingUsing“Hashing”isbetterthanstringmatching!Benefitofclassificationnolongerexistswhenusing“Hashing”!使用stringmatchingsequentialsearch:Toomuchfindingoverhead。,修改過的設計,新架構圖Folding方法,Structureof“JVMwithJIT”,Javacodesource,JAVAcompiler,Javabytecode,ClassloaderBytecodeverifier,Hardware,OperatingSystem,Javaclasslibraries,Hotspot,Interpret,Nativecode,JVM,Interpreter,JIT,Y,N,InteractionbetweenInterpreterBytecodeinformation:TypeP_num:PushnumberPostive,stackgrowC_num:PopnumberNegative,stackfall,方法(4-3)-Algorithm,經由bytecode定義可得:P-type:C_num=0,P_num=1.C-type:P_num=0,C_num=1.O-type:不一定，視其功能而定。以O-type的attribute為尋找pattern的依據。P_num:向後尋找P_num個bytecodesC_num:向前尋找C_num個bytecodes,方法(4-4),Match:向前找C_num個bytecodes的P_num剛好和O-type的C_num相抵銷。向後找P_num個bytecodes的C_num剛好和O-type的P_num相抵銷。整個pattern的attribute和要為零。無法match放棄此O-typebytecode，繼續找下一個。針對continuouspattern設計。,未來進度,TracingcodeModifyingcodeSimulationPerformance,Tracingcode,EnvironmentconfigurationTracecodeConcentrateon“HowtoaddFoldingintoJIT?”,Modifyingcode,AddingFoldingtoJITModulizingFoldingandaddingitintoJITbetween“IRgenerator”and“Codegenerator”,IRGenerator,CodeGenerator,Bytecode,Nativecode,Folding,Simulation,RunbenchmarkonARMsimulatoronLinuxworkstationBenchmark:”EmbeddedCaffeineMark”,Performance,Findout“PerformanceSpeedup”afterusingfoldingSpeedup=(time_with_folding)/(t