Finding the cache block size

Question

How do I find the cache block size in Ubuntu, programmatically (with C++) or otherwise?

Answer 1

You can find it in /proc/cpuinfo; cache size for the total size, and cache_alignment for the block size.

Answer 2

One way is to fill an std::vector or just a plain array with random values, and do something simple, e.g. square each element in a loop. Then measure the execution time as a function of the vector length. You'll very clearly see a jump in the exec time once your vector does not fit into the cache.