“与主存储器同步”是什么意思？

Question

短语“ synchronization with main memory ”是什么意思？

Answer 1

When you have multiple threads each thread may keep a local copy of a variable's value. However the "official copy" of the value is kept in main memory. So what that phrase means is that any local copy of a variable's value will be made consistent with main memory (either reading to check for updates, or writing to publish updates made to the local copy).

Answer 2

http://www.javamex.com/tutorials/synchronization_concurrency_synchronized2.shtml

Answer 3

Synchronization helps to create read and write barriers. ie it establishes a boundary whereby you can be assured that whatever be the order of operations (read/write) there will be a 'happens-before' relationship between them. It makes it obvious for the processor to flush out all changes in local (cache/register) copies of objects under synchronization to the main memory, in the meanwhile giving no access to that particular memory instance under synchronization.