Distributed Software Transactional Memories - Distributed Systems ...

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Basic Concepts ! In the past: ! More performance via faster CPUs ! Now: ! More performance via more CPUs ! Concurrent programming has to become mainstream M. Couceiro, P. Romano, L. Rodrigues, HPCS 2011
Basic Concepts ! Ideally ! Performance would scale linearly with the number of cores ! (with 8 cores we would have a program 8 times faster) ! Reality: ! Speed up limited by % serial code ! Small % can kill performance (Amdahl’s Law) ! Say 25% of the program is serial ! 8 cores = 2.9 speedup. M. Couceiro, P. Romano, L. Rodrigues, HPCS 2011
Page 1 and 2: Distributed Software Transactional
Page 3 and 4: Contents ! Part I: (Non-Distributed
Page 5: Basic Concepts ! Concurrent program
Page 9 and 10: Basic Concepts ! Ideally ! Performa
Page 11 and 12: Explicit synchronization ! One of t
Page 13 and 14: Fine Grained Parallelism? ! Very co
Page 15 and 16: Abstractions for simplifying concur
Page 17 and 18: Transactional Memories ! Hide away
Page 19 and 20: TMs: where we are, challenges, tren
Page 21 and 22: Run-time ! How does it work? ! The
Page 23 and 24: Example of optimistic concurrency c
Page 25 and 26: Many, many, variants exist ! For in
Page 27 and 28: How to choose? ! What is a correct
Page 29 and 30: Theoretical Foundations ! Safety: !
Page 31 and 32: Histories ! The execution of a set
Page 33 and 34: Histories ! Two transactions are se
Page 35 and 36: Histories ! A history is sequential
Page 37 and 38: Histories ! A history is sequential
Page 39 and 40: Histories ! Two histories are equiv
Page 41 and 42: What the programmer wants? ! Progra
Page 43 and 44: Serializability ! Serializable? WO1
Page 45 and 46: Serializability ! Serializable? WO1
Page 47 and 48: Opacity ! Serializable (blue aborts
Page 49 and 50: Opacity ! In a database environment
Page 51 and 52: Opacity: example Initially: x:=1; y
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! Intuitive definition: Opacity [GK
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Does classic optimistic concurrency
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Progress ! STMs can abort transacti
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Conditional progress: obstruction f
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Contention-managers Let TA be execu
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CM: Backoff Let TA be executing and
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CM: Greedy Let TA be executing and
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(Non-Distributed) STMs ! Basic Conc
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DSTM ! Killer write: ! Ownership. !
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DSTM - Reads and Validation ! Concu
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DSTM - Why is careful read needed?
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JVSTM ! Java Versioned Software Tra
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JVSTM - Versioned boxes B body: ! V
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JVSTM - Algorithm ! Upon write, jus
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Contents ! Part I: (Non-Distributed
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Origins ! Convergence of two main a
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DSTMs vs DSM ! DSTMs are simpler to
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DSTMs vs DBMS ! Transactions are of
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Goals ! Better performance: ! Doing
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Distribution Strategies ! Single Sy
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Distributed STMs ! Origins ! Goals
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Control Flow Model ! Data is static
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Toolbox ! Atomic Commitment ! Unifo
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2-phase commit coordinator particip
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3PC coordinator participant partici
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Uniform Reliable Broadcast ! Allows
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Atomic Broadcast ! Reliable broadca
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Abcast with optimistic delivery ! T
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ABcast with optimistic delivery fin
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Replicating a single lock ! In abse
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Replicating a single lock T1 lock()
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Single-phase schemes ! State machin
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State-machine replication AB of T1
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Primary-backup ! Write transactions
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Multi-master ! Two transactions may
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Non-voting ! The transaction execut
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Voting R1 Execution Transaction T1
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Part III: Case-Studies ! Partitione
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Cluster-STM ! Software Transactiona
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Cluster-STM (a) increment ( proc t
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Cluster-STM increment local ( proc
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Cluster-STM ! Read locks (RL) vs. r
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Cluster-STM ! Write buffering: two
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Cluster-STM: Graph Analysis (SSCA2)
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Sinfonia ! Sinfonia: A new paradigm
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SA † VMware, Palo Alto, CA, USA S
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... Min API write items mem-id mem-
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30 if action then apply writems 31
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D 2 STM ! Non-voting replication sc
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D 2 STM AB of both T1’s readset &
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D 2 STM M. Couceiro, P. Romano, L.
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D 2 STM ! False Positives: ! An ite
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D 2 STM ! Write transaction T: ! Lo
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D 2 STM ! STMBench7: Results M. Cou
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ALC ! Asynchronous Lease Certificat
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ALC ! Transactions are locally proc
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ALC P1 Lease Request (AB) Lease Ens
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ALC P1 Lease Request Lease Ensured
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ALC P1 Lease Request Apply Lease En
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ALC Application Distributed STM API
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ALC ! Synthetic “Worst case” sc
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Basic Active Replication Atomic Bro
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Improvement Atomic Broadcast Tx Exe
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Speculative Opt Atomic Broadcast Tx
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AGGRO Algorithm upon opt-Deliver(Ti
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AGGRO Algorithm upon read(Ti, X) if
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AGGRO Algorithm upon abort(Ti) abor
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Contents ! Part I: (Non-Distributed
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Conclusions ! No technique outperfo
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CLOUD-TM ! DTMs: a programming para
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Euro-TM Cost Action ! Research netw
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Bibliography ! [BAC08] Robert L. Bo
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Bibliography ! [GHP05] Rachid Guerr
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Bibliography ! [KAJLKW08] Christos
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The End Thank you. M. Couceiro, P.
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