The top 500 supercomputers of Planet Earth all use Linux. This has been the case for some time now. Naturally, performance share for Linux is 100%. Indeed, it is great to see Linux dominate the high performance computing platform.
Processors from Intel are commonly used and IBM’s Power9 processors are used as well though not as common. Note, however, that the top 2 supercomputers, Summit and Sierra, use Power9 processors running Red Hat Enterprise Linux.
GPUs are also installed in some of the supercomputers as coprocessors. Nvidia cards are usually the choice for the GPU coprocessors, probably due to the vast amount of software supporting Nvidia GPUs for computational tasks. The Summit and Sierra supercomputers use the Nvidia Volta GV100 as coprocessors.
You can generate list statistics for the top 500 supercomputers at this link: https://www.top500.org/statistics/list/