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CMU CS 15410 - Lecture

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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 2715-410, S’04- 1 -ReviewApr. 30, 2004Dave EckhardtDave EckhardtBruce MaggsBruce MaggsL38_Review15-410“...This is a transformative class...”15-410, S’04- 1 -SynchronizationP3 grading guidanceP3 grading guidanceWeights are approximate~70% shell works (no horrible hacks)~70% shell works (no horrible hacks)~20% tests~20% testsP3/P4 hurdle testsOther tests~10% structure/style~10% structure/style15-410, S’04- 1 -SynchronizationExam will be closed-bookExam will be closed-bookBut you may bring a 1-sided 8.5x11 sheet of notes6 point font or larger :-)Weakly non-cumulativeEmphasis on new material, design questionsYou will need to use some “old” knowledgeWe didn't really test on “P2 knowledge” (nor P3)15-410, S’04- 1 -SynchronizationFaculty evaluation formsFaculty evaluation formsAbout today's “review”About today's “review”More “reminders” than “course outline”Un-mentioned topic implies “text & lectures straightforward”Reading some of the textbook is advisable!15-410, S’04- 1 -Read Your CodeRe-read your P2Re-read your P2Re-read your P3Re-read your P3Go over feedbackGo over feedbackTalk about them with your partnerTalk about them with your partnerSchedule a timeYou should understand “the hard parts”You should understand “the hard parts”Focus on whichever part you know least well(or fear the most)15-410, S’04- 1 -“Concept” LecturesWe could ask a questionWe could ask a questionWe would give you some guidance/refresh your memoryExamplesExamplesAdvanced Disk SchedulingOS StructuresPlan 9Distributed clocks15-410, S’04- 1 -Core “Phase I” conceptsMachine modelMachine modelRegisters“regular”“special”Interrupt (vs. exception – how they differ, why)Process modelProcess modelYou should be a memory-map expertKernel space, user space, virtual memoryProcess vs. threadExactly what goes on a stack, where it comes from...15-410, S’04- 1 -Core “Phase I” conceptsMutual exclusionMutual exclusionmutex, cvar, what's inside, whyConcurrencyConcurrencyRace-condition expert!DeadlockDeadlockIngredientsVarious approaches to coping15-410, S’04- 1 -Virtual MemoryJobJobMaintain multiple illusions (aka “address spaces”)PlayersPlayersHigh-level info (COW, who uses which region)Mapping data structure (maybe chosen by processor)TLB – cache of v-to-p translations from that data structure“flush” - when, why, how?Game FeaturesGame FeaturesMappings are sparseThis explains the ways they're implemented15-410, S’04- 1 -Memory HierarchyWhy we must lieWhy we must lieWhy we can get away with itWhy we can get away with itLayering (“Pyramid of deception”)Layering (“Pyramid of deception”)Why layers can't be implemented the same wayLine size, placement, write-back, ...Line size, placement, write-back, ...Caches OS's typically manageCaches OS's typically manageCoherenceCoherence15-410, S’04- 1 -SchedulingRound-RobinRound-RobinThings people doThings people doMulti-level feedback queuesDubiousDubiousPriority““Priority Inheritance”Priority Inheritance”15-410, S’04- 1 -Disk schedulingSpinning platter/waving arm modelSpinning platter/waving arm modelSeek time vs. rotational latencySeek time vs. rotational latencyFCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK, SPTF, FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK, SPTF, WSPTFWSPTFFairness, mean response time, variance, starvationFairness, mean response time, variance, starvationFreeblock schedulingFreeblock schedulingConcept15-410, S’04- 1 -Disk Array OverviewHistorical practicesHistorical practicesStriping, mirroringThe reliability problemThe reliability problemMore disks  frequent array failuresCannot tolerate 1/N reliabilityParity, ECC, why parity is enoughParity, ECC, why parity is enoughErasure channelsGood terminology to display at parties15-410, S’04- 1 -Disk Array OverviewRAID “levels” (really: flavors)RAID “levels” (really: flavors)Understand RAID 0, 1, 4 vs. 5What they're good for, why15-410, S’04- 1 -File SystemsData access modelData access modelWhat it means for a file to be “open”Cache issuesCache issuesNamingNamingDirectory flavors, mountingCore problem: block mappingCore problem: block mappingCompare data structures to VM“Holes”ArchitectureArchitectureLayering to support multiple file system types, ...15-410, S’04- 1 -Distributed File SystemsClient-side redirectionClient-side redirectionWhich files are remote? How to operate remotely?CommunicationCommunicationRPC, XDRFlow of RPC operations to access a fileMount, lookup, accessBatching (what, why)Cache vs. consistency vs. locks15-410, S’04- 1 -IPCCommunicating process on one machineCommunicating process on one machineNamingNamingName server?File system?Message structureMessage structureSender id, priority, typeCapabilities: memory region, IPC rightsSynchronization/queueing/blockingSynchronization/queueing/blocking15-410, S’04- 1 -IPCGroup receiveGroup receiveCopy/share/transferCopy/share/transferA Unix surpriseA Unix surprisesendmsg()/recvmsg() pass file descriptors!15-410, S’04- 1 -RPC OverviewRPC = Remote RPC = Remote Procedure CallProcedure CallExtends IPC in two waysExtends IPC in two waysIPC = Inter-Process CommunicationOS-level: bytes, not objectsIPC restricted to single machineMarshallingMarshallingServer locationServer location15-410, S’04- 1 -RPC OverviewCall semanticsCall semanticsAsynch? Batch? Net/server failure?Client flow, server flowClient flow, server flowCleint stub routines, server dispatch skeletonJava RMIJava RMI(have some sense—obviously, we didn't make you use it)15-410, S’04- 1 -MarshallingValues must cross the networkValues must cross the networkMachine formats differMachine formats differSerialize/de-serializeFormat/packingType mismatch issues““The pointer problem”The pointer problem”15-410, S’04- 1 -Protection OverviewProtection vs. SecurityProtection vs. SecurityInside vs. outside “the box”Objects, operations, domainsObjects, operations, domainsAccess control Access control (least privilege)(least privilege)3 domain models3 domain


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CMU CS 15410 - Lecture

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