REP-1994-143 - AC om pa r isono fF astandLowO verheadD istr...

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Unformatted text preview: AC om pa r isono fF astandLowO verheadD istr ibu tedP r io r ity Lock s TheodoreJohn sonandR ichardN ewm an-W o lfe D ep t .o fC IS ,U n ivers ityo fF lor ida G a inesv ille ,F l- [email protected] c is .u .edu ,nem [email protected] c is .u .edu A b stract D istr ibu tedsynch ron izat ion isnecessarytocoord inatethed iverseact iv it ieso fad istr ibu ted sy stem .P r ior itysynch ron izat ion isneeded forrea lt im esy stem s ,orto im p rovetheperform ance o fcr it ica ltask s .P ract ica lsynch ron izat iontechn iquesrequ irefastrespon seand lowoverhead .In th ispaper ,w ep resen tth reep r ior itysynch ron izat iona lgor ithm sthatsend O ( log n )m essagesper cr it ica lsect ionrequest ,andu se O ( log n )b itso fstorageperp rocessor .Tw oo fthea lgor ithm sare basedonL iandH udak 'spathcom p ress iontechn iques ,andtheth irda lgor ithm u sesR aym ond 's xed-treestructu re .S inceeacho fthea lgor ithm shavethesam etheoret ica lcom p lex ity ,w em ake aperform ancecom par isontodeterm inewh icho fthea lgor ithm sisbestunderd ieren tload s andd ieren trequestp r ior ityd istr ibu t ion s .W endthatwhentherequestp r ior ityd istr ibu t ion isstat ionary ,thepath-com p ress iona lgor ithm thatu sesas ing ly-linked listisbestovera ll,bu t thethexed-treea lgor ithm requ iresfew erm essageswhenthenum bero fp rocessorsissm a lland theload ish igh(% orgreater) .W hentherequestp r ior ityd istr ibu t ion isnon-stat ionary , thexed-treea lgor ithm isrequ iresthefew estm essageswhentheload is % orgreater . The doub le-linka lgor ithm isbetterwhentheload islow ( lessthan % ) ,orifm in im iz ingexecu t ion t im eoverhead ism oreim portan tthanm in im iz ingm essageoverhead . In troduct ion D istr ibu tedsynch ron izat ion isan im portan tact iv itythatisrequ iredtocoord inateaccesstoshared resou rcesinad istr ibu tedsy stem .A seto f n p rocessorssynch ron izethe iraccesstoasharedresou rce byrequest inganexc lu s ivep r iv ilegetoaccesstheresou rce .T hep r iv ilegeiso ftenrep resen tedasa token .R ea lt im esy stem s ,orsy stem sthathavecr it ica ltask sthatm u stexecu tequ ick lyforgood perform ance ,needp r ior it izedsynch ron izat ion .Inp r ior itysynch ron izat ion ,everyrequestforthe tokenhasap r ior ityattached .W henthetokenho lderre leasesthetoken ,itshou ldbeg iventothe p rocessorw iththeh ighestp r ior ityrequest . Inth ispaper ,w ep resen tth reed istr ibu tedp r ior itysynch ron izat iona lgor ithm s ,eachrequ ir ing O ( log n )b itso fstorageperp rocessor(the O ( log n )b itsarerequ iredtostorethenam eso f O () p rocessors) ,and O ( log n )m essagespercr it ica lsect ionen try .T helow spaceandm essagepass ing overheadm akethem sca lab leandp ract ica lforim p lem en tat ion .T hep rocessorssynch ron izeby send ingand in terp ret ingm essagesaccord ingtoasynch ron izat ionp rotoco l.W eassum ethatevery m essagethatissen tiseven tua llyrece ived .T heth irdp rotoco la lsorequ iresthatm essagesare W eacknow ledgethesupporto fU SRAgran t#-andN SFgran tDM S- de livered intheordersen...
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