REP-1994-131 - AF astandLowO verheadD istr ibu tedP r io r...

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Unformatted text preview: AF astandLowO verheadD istr ibu tedP r io r ityLock 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- ted@ c is .u .edu ,nem o@ 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 .W ep resen tad istr ibu tedp r ior ity lockthatu sesL iandH udak 'spathcom p res- s ionm ethod stoach ieveatheoret ica l O ( log n )m essagespercr it ica lsect ionrequest ,where n is thenum bero fp rocessors .Inadd it ion ,ou ra lgor ithm requ ireson ly O ( log n )b itso fstorageper p rocessor ,bym ak ingu seo fd istr ibu ted lists .W ep resen tperform anceresu ltstoshow thatthe expectedm essagecom p lex ityo fthea lgor ithm isindeed O ( log n )percr it ica lsect ionrequest . Thelow storageandoverheadrequ irem en tso fthea lgor ithmm akeitsca lab leandp ract ica lfor im p lem en tat ion .Inadd it iontoitsu seinsynch ron izat ion ,ou ra lgor ithm hasapp licat ion sto d istr ibu tedsharedv irtua lm em orycon s istencyw ithnove lcheck-in/check-ou tsem an t ics . 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 . T hep rocessessynch ron izebysend ingand in terp ret ingm essagesaccord ingtoasynch ron izat ion p rotoco l.W eassum ethateverym essagethatissen tiseven tua llyrece ived ,bu tthatm essagescan berece ivedou to forder . Inth ispaper ,w ep resen tad istr ibu tedp r ior itysynch ron izat iona lgor ithm thatrequ ires O ( log n ) b itso fstorageperp rocessor(the O ( log n )b itsarerequ iredtostorethenam eso f O ()p rocessors) . T hea lgor ithmu sesthepathcom p ress iontechn iqueo fL iandH udak toob ta inatheoret ica l O ( log n )m essagesperrequest .O u rperform anceresu ltsshow that O ( log n )m essagesarerequ ired W eacknow ledgethesupporto fU SRAgran t#-andN SFgran tDM S- inp ract ice .T helow spaceandm essagepass ingoverheadm akeitsca lab leandp ract ica lforim p le- m en tat ion . C on s iderab leatten t ionhasbeenpa idtothep rob lem o fd istr ibu tedsynch ron izat ion .Lam port p roposesat im estam p-basedd istr ibu tedsynch ron izat iona lgor ithm .Ap rocessorb roadcastsits requestforthetokentoa llo ftheotherp rocessors ,w h ichrep lyw ithaperm iss ion .Ap rocessor im p lic it lyrece ivesthetokenw hen itrece...
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REP-1994-131 - AF astandLowO verheadD istr ibu tedP r io r...

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