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Chapter 1. Processor Cores

A processor core is a physical Central Processing Unit (CPU) in a computer. Cores are responsible for executing machine code. A socket is the connection between the processor and the motherboard of the computer. The socket is the location on the motherboard that the processor is placed into. A single core processor physically occupies one socket, and has one core available. A quad-core processor physically occupies one socket and has four cores available.
When designing realtime applications, take the number of available cores into account. It is also important to note how caches are shared among cores, and how the cores are physically connected.
If multiple cores are available to the application, use threads or processes to take advantage of them. If a program is written without using these constructs, it will only run on one processor at a time. A multi-core platform allows advantages to be gained through using different cores for different types of operations.

1.1. Caches

Often, the various threads of an application will need to synchronize access to a shared resource, such as a data structure. Performance can be improved in this case by knowing the cache layout of the system. The Tuna tool can be used to help determine the cache layout. Try binding interacting threads to cores, so that they share the cache. Cache sharing reduces memory faults by ensuring that the mutual exclusion primitive (mutex, condvar, or similar) and the data structure itself use the same cache.