Specification and management of QoS in real-time databases s(8)

The95percentconfidenceintervalsofatearelessthan½ateÀ2:1%;ateþ2:1% .ForBaseline-1andBaseline-2,theateincreasesastheloadincreases,violatingthereference,ater,atloadsexceeding175percent.InthecaseofPC-ATEEDF,atereachesthereferenceat150percentof

5.Wehavenotobservedanydeadlinemisses.

Abstract—Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services that are provided

AMIRIJOOET

AL.:SPECIFICATIONANDMANAGEMENTOFQOSINREAL-TIMEDATABASESSUPPORTINGIMPRECISECOMPUTATIONS315

Fig.5.Experiment2:Averageperformancewhenvaryingexecutiontimeestimationerror.(a)PC-MPUandPC-MP.(b)PC-ATE.

appliedload.ForPC-ATEHEFandPC-ATEHEDF,atereachesthereferenceat175percent.AllPC-ATEalgorithmsprovidearobustperformancesinceateiskeptatthespecifiedreferenceduringoverloads.

Consideringsdte,the95percentconfidenceintervalsforallalgorithmsarelessthan½sdteÀ1:92%;sdteþ1:92% .Forallalgorithms,sdteincreasesasloadandateincrease.At200percentload,thecorrespondingsdteforPC-ATEEDF,PC-ATEHEDF,andPC-ATEHEFis34.1percent,25.2percent,and18.2percent,respectively.Consequently,deviationoftransactionerrorisminimizedwhenHEFschedulingisused.Itisworthmentioningthat,underHEFscheduling,sdteislessasresourcesareallocatedwithregardtotransactionerrors,while,underEDFscheduling,resourcesaredistributedwithregardtodeadlines.UnderEDFscheduling,twotransactionswithdeadlinesneareachothermayreceivedifferentamountsofresourcesand,hence,theymayterminatewithasignificantdeviationintransactionerror,while,inthesamecase,underHEFscheduling,theresourcesaredividedsuchthatbothtransactionsterminatewithtransactionerrorsclosetoeachother.

The95percentconfidenceintervalsofmdearelessthan½mdeÀ0:13%;mdeþ0:13% .StartingwithFig.4a,theaveragemdeforBaseline-1andBaseline-2violatesthereferencemdesetto2percent.Incontrast,inthecaseofPC-MPU,mdeissignificantlylowerthanmder.Sincethemisspercentagesarekeptlowatalltimes,theyarenotlikelytoovershoot.Consequently,thecontrolsignalfromthemisspercentagecontrollersislikelytobepositive,whichisinterpretedbytheQoDmanagerasaQoDupgradeand,hence,mdewillnotreachthelevelofmder.ThisisfurtherexplainedinSection5.6,wherethetransientperformanceofthealgorithmsisdiscussed.PC-MPpro-videsanaveragemdeclosertomder,givenby1:78Æ0:024%atloads150percentand200percent.However,mdedoesnotreachmdersincemdeissetaccordingtomO(whichdoesnotreachmOr).TurningtoFig.4b,the95percentconfidenceintervalsofmdearelessthan½mdeÀ0:5%;mdeþ0:5% .TheaveragemdeforBaseline-1andBaseline-2violatesthereferencemdesetto5percentatappliedloadsof175percentand130percent,respectively.Incontrast,inthecaseofPC-ATEEDF,PC-ATEHEF,andPC-ATEHEDF,mdeisatthereferenceduringoverloads.

TheexperimentshaveshownthatPC-MPUproducesamisspercentagesignificantlylowerthanthespecifiedmisspercentagesand,hence,itdoesnotfullysatisfythegivenQoSspecification.PC-MP,ontheotherhand,producesmisspercentagesclosetothegivenreferencesand,consequently,thegivenQoSspecificationissatisfiedwithregardtosteady-stateperformance.WehavealsoseenthatPC-ATEHEF,PC-ATEHEDF,andPC-ATEEDFarerobustagainstvaryingappliedloads.Moreover,PC-ATEHEFoutperformstheotheralgorithmswithregardtoQoSfairnessofadmittedtransactions.

5.5Experiment2:ResultsofVaryingesterr

Weapply200percentloadandvarytheexecutiontimeestimationerroraccordingtoesterr=0.00,0.25,0.50,0.75,and1.00.ControllerstunedusingSTAareused.Fig.5aandFig.5bshowtheperformanceofPC-MPU,PC-MP,PC-ATEHEF,PC-ATEHEDF,andPC-ATEEDF.Dash-dottedlinesindicatereferences.

AsinExperiment1,mMiszeroforallapproachesandesterr.TurningtomO,the95percentconfidenceintervalsforallalgorithmsarelessthan½mOÀ2:7%;mOþ2:7% .Asexpected,Baseline-1andBaseline-2donotsatisfytheQoSspecification,whereasPC-MPUandPC-MPareinsensitiveagainstvaryingesterr,asmOandmdedonotchangeconsiderablywhenvaryingesterr.Studyingate,wenotethatBaseline-1andBaseline-2donotsatisfytheQoSspecificationasatereaches52percentwhenesterrequals1.The95percentconfidenceintervalsforPC-ATEalgo-rithmsarelessthan½ateÀ0:3%;ateþ0:3% .PC-ATEEDF,PC-ATEHEF,andPC-ATEHEDFareinsensitiveagainstvaryingesterrasateandmdedonotchangewithvaryingesterr.Fromtheabove,wecanconcludethatPC-MPU,PC-MP,PC-ATEHEF,andPC-ATEHEDFareinsensitivetochangestoexecutiontimeestimationand,hence,theycaneasilyadaptwhenaccurateruntimeestimatesarenotknown.

5.6Experiment3:TransientPerformance

Studyingtheaverageperformanceisoftennotenoughwhendealingwithdynamicsystemsand,therefore,westudythetransientperformanceofPC-MPU,PC-MP,PC-ATEHEF,PC-ATEHEDF,andPC-ATEEDF.Wesetloadto200percentandesterrto1.

Abstract—Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services that are provided

316IEEETRANSACTIONSONCOMPUTERS,VOL.55,NO.3,MARCH

2006

Fig.6.Experiment3:Transientperformance.(a)PC-MPU.(b)PC-MP.(c)PC-ATEEDF.

TABLE1

JsandJawith95PercentConfidence

Intervals

5.6.1ResultsofControllersTunedUsingSTA

Fig.6a,Fig.6b,andFig.6cshowthetransientbehaviorofPC-MPU,PC-MP,andPC-ATEEDFwithcontrollerstunedusingSTA.WerefertoTable1forasummaryoftheperformanceofPC-ATEHEF,PC-ATEHEDF,andPC-ATEEDFwithcontrollertunedusingSTAandDYN.Thedash-dottedlineindicatesthereference,whilethedottedlineindicatesmaximumovershoot.Forallalgorithms,mOandateovershootsdecayfasterthan60s,whichislessthanthesettlingtimerequirementgivenintheQoSspecification.StartingwithPC-MPU,wecannotethatmOiskeptlowatalltimes.ThisisexpectedsincetheaveragemOwasshowntobelow.Thereadermayhavenoticedthatmdeisgreaterthanzerointheinterval20-150,wheremOiszero.Sincemdeisgreaterthanzero,itisclearthat lERmaybecomenegativeduringthatpe …… 此处隐藏：6280字，全部文档内容请下载后查看。喜欢就下载吧 ……