And programs are synchronized compiler could not

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: zed (GOOD PROGRAMS!) – Models characterized by their attitude towards: RAR, WAR, RAW, WAW to different addresses ff 52 Relaxed Consistency Models: The Basics • Key idea: allow reads and writes to complete out of order, but use synchronization operations to enforce ordering a synchronized program behaves as if the processor were if th sequentially consistent – By relaxing orderings, may obtain performance advantages – Also specifies range of legal compiler optimizations on shared data – Unless synchronization points are clearly defined and programs are synchronized, compiler could not interchange read and write of 2 shared data items because might affect the semantics of the program • 3 major sets of relaxed orderings: 1. W→R ordering (all writes completed before next read) (all writes completed before next read) • Retains ordering among writes many programs that operate under sequential consistency operate under this model, without additional synchronization. Called processor consistency 2. W → W ordering (all writes completed before next write) (all writes completed before next write) 3. R → W & R → R orderings, a variety of models depending on ordering restrict...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online