[rbanffy]

The cores are individually slow and non-parallel code will not be fast, but the Airmont architecture it's based on is an out-of-order core, so it's not that bad as earlier versions of the Phi, plus it has up to 16GB of very fast HMC memory near the cores, helping make up for the slow cores with less costly cache misses than an ordinary Xeon. It also has four threads per core without the penalties of earlier Phis. Single-thread stages will suffer but that may end up being compensated by ridiculously parallel compilation stages.

But yes. The Phi is designed to shine with code that uses its AVX512 units. Compiling the Linux kernel is a "create misuse" of its technology. One I'd like to try one day ;-)