209 - fast-code-is-always-in-fashion

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1、WebLanguagesandVMsorwhyfastcodeisalwaysinfashionLarsBak&KasperLundSoftwareEngineersatGoogleInc.HackingonVMssidebysidethelast13years...SoWhyAreWeHere?SpeedfuelsapplicationinnovationWebbrowsersarefasterthanever,butaretheyfastenough?WewillconvinceyouthatDarttakesperformancetothenextlevelRe

2、membertheBrowsersof2006?199820002002200520062008Firefox2.0InternetExplorer7.0Safari2.0Opera9.0BrowserPerformanceBeliefsin2006Browserswerebelievedtobe"fastenough"●WebappslikeGmailandGoogleMapsranfine●JavaScriptwasinherentlytooslowforheavyclientsidecomputations●JavaScriptexecutionwasnotpe

3、rceivedasabottleneckPerformancewasevaluatedusingmicro-benchmarks●Emphasiswasputonloopsandsimplearithmetic●DynamicdispatchingandmemorymanagementweresadlyneglectedSunSpider:bitwise-andBenchmarkfromSunSpiderversion0.9.1JavaScriptbitwiseAndValue=4294967296;for(vari=0;i<600000;i++)bitwiseAnd

4、Value=bitwiseAndValue&i;SunSpider:bitwise-andBenchmarkfromSunSpiderversion0.9.1JavaScriptbitwiseAndValue=4294967296;for(vari=0;i<600000;i++)bitwiseAndValue=bitwiseAndValue&i;...butthisalwaysyieldszero?SunSpider:bitwise-andBenchmarkfromSunSpiderversion1.0JavaScriptbitwiseAndValue=4294967

5、296;for(vari=0;i<600000;i++)bitwiseAndValue=bitwiseAndValue&i;if(bitwiseAndValue!=0)throw"ERROR:badresult...";...andthisalwaysyieldszero!V8DesignChoice:WhattoOptimizeFor?(1)Optimizeforcurrentappsandbenchmarks●Simpleandincrementalapproach●Attempttomakethings10%better(2)Optimizefortheapps

6、ofthefuture●Supportheavyclientsidecomputations●Turnthebrowserintoascalableapplicationplatform●EnablesanewclassofwebappsV8BenchmarkSuiteConsistsofbenchmarksthatare●Structuredandmostlyobject-oriented●Designedtopushthelimits●ProvenvaluableinthecontextofotherlanguagesMeasurestheperformanceo

7、f●Dynamicmethodcallsandpropertyaccesses●Memorymanagement●ClosurecreationandinvocationUp,UpandAway!Performanceimprovementsfrom2006-2013●JavaScriptexecutesmorethan100xfaster●AverageheapsizesareupandGCpausesaredown●BenchmarknumbersarefrequentlyreportedinthepressWebappshavebecomehu