Using Kilim's isolation types for multicore efficiency

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Why can a program run slower on multicore? UNIVERSITYOF CAMBRIDGE • CPU1 writes a cache line ⇒ data in CPU2’s cache is discarded. • CPU2 now writes this cache line ⇒ the line must be reloaded (even from memory) and data in CPU1’s cache discarded. • A two-core version of virtual memory ‘thrashing’ (or of repeated cache reloading in naive big-matrix multiplication). It’s harmless (or even good) if two threads running on the same processor core both access a cache line (since all accesses will hit the cache), but . . . it’s bad if two threads running on different processor cores access the same cache line. Program runs slower on two cores than one! Multicore cache model is like multiple-reader/single-writer . . . Using Kilim’s isolation types for multicore efficiency 16 FoVeOOS’2011
How should we react? Shared memory and parallelism is problematic: • hard to write correct code (locks, mfence etc. needed) • sequential consistency surprises in semantics • cache effect surprises in performance UNIVERSITYOF CAMBRIDGE But lots of these problems go away if the programmer knows when shared data is logically being transferred between cores. Type systems (richer than usual) can express and enforce this . . . Using Kilim’s isolation types for multicore efficiency 17 FoVeOOS’2011
Page 1 and 2: UNIVERSITYOF CAMBRIDGE Using Kilim
Page 3 and 4: The big picture • Traditional obj
Page 5 and 6: Why does multi-core affect things?
Page 7 and 8: • an example • modern hardware
Page 11 and 12: Multi-core and sequential consisten
Page 13 and 14: Multi-core hardware semantics (2) I
Page 15: Multi-core-chip memory models Today
Page 19 and 20: Caches are multiple-reader/single-w
Page 23 and 24: Type Systems - weakness UNIVERSITYO
Page 25 and 26: Classical and Linear Type Systems (
Page 27 and 28: Substructural type systems (WEAKEN)
Page 29 and 30: An algebra of capabilities UNIVERSI
Page 31 and 32: From algebra to algorithm UNIVERSIT
Page 35 and 36: Kilim qualifiers UNIVERSITYOF CAMBR
Page 37 and 38: Core Kilim syntax FuncDcl ::= free
Page 39 and 40: Kilim isolation type checking Many
Page 41 and 42: One neat point UNIVERSITYOF CAMBRID
Page 43 and 44: What I didn’t say about Kilim UNI
Page 45: Conclusions • multi-core works be

Using Kilim's isolation types for multicore efficiency

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