Everything you always wanted to know about synchronization but were afraid to ask-ppt

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1、EverythingYouAlwaysWantedtoKnowaboutSynchronizationbutWereAfraidtoAskTudorDavid,RachidGuerraoui,VasileiosTrigonakisThemulti-corerevolution•Bigchallengesinhardware&software•Software–scalability:↑performanceby↑numberofcoresSynchronizationisoneofthebiggestscalabilitybottlenecks11/4/2013Vas

2、ileiosTrigonakis(EPFL)2Synchronization•Cannotalwaysbeavoided–notallapplicationsembarrassinglyparallel•Synchronizationisjustanoverhead–butguaranteescorrectness•Scalabilityofsynchronization–donot↓performanceasthenumberofcores↑Scalabilityofsynchronizationiskeytoapplicationscalability11/4/2

3、013VasileiosTrigonakis(EPFL)3Synchronizationisdifficult•Tonsofwork–designofsynchronizationschemes[ISCA’89,TPDS’90,ASPLOS’91,TOCS’91,PPoPP’01,PODC’95,ICPP’06,SPAA’10,IPDPS’11,PPoPP’12,ATC’12,…]–fixsynchronizationbottlenecks[SOSP’89,HPCA’07,OSDI’99,OSDI’08,SOSP’09,APLOS’09,OSR’09,OSDI’10,

4、…]•Scalabilityissues?–hardware–usageofspecificatomicoperations–synchronizationalgorithm–applicationcontext–workloadLimitedunderstandingofthebehaviorofsynchronization11/4/2013VasileiosTrigonakis(EPFL)4TakeastepbackandperformathoroughanalysisofsynchronizationonmodernhardwareWhatisthemains

5、ourceofscalabilityproblemsinsynchronization?AnswerScalabilityofsynchronizationismainlyapropertyofthehardware11/4/2013VasileiosTrigonakis(EPFL)5Keyobservations1.Crossingsocketsisakillerccccccccccccsocketsocket2.Sharingwithinasocketisnecessarybutnotsufficientcccccccccccc3.Intra-socketunif

6、ormitymattersccccccccccccccccccccccDirectoryvs.cccccccccccccccccccccc4.Loads&storescanbeasexpensiveasatomicoperations5.Simplelocksarepowerful…11/4/2013VasileiosTrigonakis(EPFL)6DisclaimerWedonotclaim“Badsynchronization”insoftwarewillscalewellduetohardwareWeclaim“Goodsynchronization”ins

7、oftwaremightnotscaleasexpectedduetohardware11/4/20137AnalysismethodHardwareprocessorsSynchronizationlayersccccccccccccccccccccccccsystems/applicationscccccccccccccccccc(e.g.,hashtable)Multi-socketsccccccsoftware•AMDOpteron(4x6172-48cores)softwareprimitives•IntelXeon(8xE7-8867L-