Distributed shared memory
This presentation is the property of its rightful owner.
Sponsored Links
1 / 10

Distributed Shared Memory PowerPoint PPT Presentation


  • 122 Views
  • Uploaded on
  • Presentation posted in: General

Distributed Shared Memory. Distributed Shared Memory. Middleware Memory that is distributed and duplicated appears local and as single copy Hides complexity. Designing DSM. Data structure (byte, object, immutable) Synchronization constructs Consistency model (ordering of updates)

Download Presentation

Distributed Shared Memory

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Distributed shared memory

Distributed Shared Memory


Distributed shared memory1

Distributed Shared Memory

  • Middleware

  • Memory that is distributed and duplicated appears local and as single copy

  • Hides complexity


Designing dsm

Designing DSM

  • Data structure (byte, object, immutable)

  • Synchronization constructs

  • Consistency model (ordering of updates)

  • Update options (update or invalidate)

  • Granularity

  • Thrashing


Memory consistency models

Memory Consistency Models

  • Defined for DSMs

  • Consider what executions could happen

  • Execution

    • Sequences of read and write operations

    • One sequence for each process in system.


Uniform consistency models

Uniform Consistency Models

  • Only have read and write operations

  • Sequential Consistency

  • Pipelined-RAM

  • Causal Consistency

  • Coherence

  • Processor Consistency


Uniform model definitions

Uniform Model Definitions

  • Sequential Consistency:

    • All processes order all writes in the same order

  • Pipelined RAM:

    • All processes order all writes in program order

  • Causal Consistency:

    • All processes order writes such that it satisfies Lamport’s happens-before relation

  • Coherence:

    • All processes order writes to the same location in the same order


Release consistency

Release Consistency

  • Hybrid Model

  • Operations available:

    • Read – read local copy

    • Write – write to local copy

    • Acquire – update local copy

    • Release – send updates of local copy

  • Acquire and Release ops are sequentially consistent


Acquire release order

Acquire-release Order

  • (O,<aro) – acquire-release order

  • o1 <aroo2 if o1 <poo2 and

    • o1 and o2 are on the same data item, or

    • o1 is an acquire, or

    • o2 is a release, or

    • There exists o st o1 <aroo and o <aroo2


Formal definition of rc

Formal Definition of RC

  • A computation is Release Consistent if

  • Each process orders its own ops, all writes, release and acquire operations

  • Such that the order satisfies the acquire-release order

  • The acquire and release ops are ordered such that

    • All processes agree on the ordering (SC)

    • Each acquire is immediately followed by its matching release.


Hybrid models

Hybrid Models

  • Distinguish between different types of memory accesses

  • Release Consistency

    • Provides acquire and release operations

  • Entry Consistency

    • Each shared variable has a lock

  • Scope Consistency

    • Variables are associated with locks automatically

  • Weak Consistency

    • Orders synchronization operations


  • Login