Thediffusionspaceofdatadiffusion architectures q JorgeBuenabad-Cha ´vez a, * ,HenkL.Muller b PaulW.A.Stallard b ,DavidH.D.Warren b a Seccio ´n de Computacio ´n, CINVESTAV, Ap. Postal 14-740, Me ´xico DF 07360, Me ´xico b Department of Computer Science, University of Bristol, Bristol BS8 1UB, UK Received7July2004;revised8September2004;accepted13September2004 Abstract Data diffusion architectures (also known as cache only memory architectures) provide a sharedaddressspaceusingphysicallydistributedmainmemorythatisassociative.Theasso- ciativenatureofmainmemorydecoupleseachaddressanditsdataitemfromanyphysical location,allowingdataitemsto diffuse,ormigrateandreplicate,inanynodeofmainmemory accordingtouse.Henceremoteaccessestendtobecomelocalaccesses,makingthedistributed organisationofmainmemorytransparenttosoftware. However, for data to diffuse effectively with reasonable performance, a fraction of main memorymustbereservedas diffusion space,toallowfordatareplicationandfreedomofdata migration.Atanymomenttheamountof distinct data residentinmainmemorymustbeless thanthecapacityofmainmemory.Otherwisedatawillkeepmovingaroundtheinterconnect mediumandmemorynodes,possiblycontinuallydisplacingdatainfrequentusebytheproc- essors,resultinginpoorperformance. Wepresentananalysisoftheissuesintheprovisionofdiffusionspaceusingempiricaldata fromarealisticenvironment.Ourexperimentalplatformisamultiprocessoremulationofa datadiffusionarchitecturethatincludesthevirtualmemorycomponentoftheMachoperating system. For flexibility in the provision of diffusion space in the context of set-associative 0167-8191/$-seefrontmatter Ó 2004ElsevierB.V.Allrightsreserved. doi:10.1016/j.parco.2004.09.001 q WorkcompletedwhileatPACT,supportedbyCONACyT50817andESPRITOMI/HORNP7249. * Correspondingauthor.Tel.:+525550613800x6552;fax:+525550613757. E-mail address: jbuenabad@cs.cinvestav.mx (J.Buenabad-Cha ´vez). www.elsevier.com/locate/parco ParallelComputing30(2004)1169–1193