What is sequentially consistent memory?
Sequential consistency is a conservative memory model that does not allow any instruction reordering on each core. This prevents many optimizations and degrades performance. However, not all memory instructions on a single core need to preserve their program order.
Why we need memory consistency explain sequential memory consistency?
HSA Memory Model Most memory consistency models, HSA included, preserve sequential semantics within a single unit of execution, thread, or agent. Sequential consistency guarantees that there is a single, globally observable, interleaving of loads, stores, and read-modify-write operations in any valid execution.
What is sequential consistency in distributed systems?
Informally, sequential consistency implies that operations appear to take place in some total order, and that that order is consistent with the order of operations on each individual process. This, combined with the total ordering property, makes sequential consistency a surprisingly strong model for programmers.
What are the different types of consistency?
Types
- Strict consistency. Strict consistency is the strongest consistency model.
- Sequential consistency. The sequential consistency model was proposed by Lamport(1979).
- Causal consistency.
- Processor consistency.
- Pipelined RAM consistency, or FIFO consistency.
- Cache consistency.
- Slow consistency.
- Release consistency.
How does the memory consistency model preserve sequential semantics?
Most memory consistency models, HSA included, preserve sequential semantics within a single unit of execution, thread, or agent. If memory operation (load, store, or read-modify-write) O1 occurs before memory operation O2 on agent A, then the effect of O1 will be visible to O2.
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Which is the best description of memory consistency?
However, memory models vary considerably in how they allow memory operations from different units of executions to interleave with one another. The most intuitive of these models is called sequential consistency.
