Windows® via C/C++, Fifth Edition

Cache Lines

If you want to build a high-performance application that runs on multiprocessor machines, you must be aware of CPU cache lines. When a CPU reads a byte from memory, it does not just fetch the single byte; it fetches enough bytes to fill a cache line. Cache lines consist of 32 (for older CPUs), 64, or even 128 bytes (depending on the CPU), and they are always aligned on 32-byte, 64-byte, or 128-byte boundaries, respectively. Cache lines exist to improve performance. Usually, an application manipulates a set of adjacent bytes. If these bytes are in the cache, the CPU does not have to access the memory bus, which requires much more time.

However, cache lines make memory updates more difficult in a multiprocessor environment, as you can ...