Cls Magic X86 ((exclusive)) Link

CLFLUSH, CLFLUSHOPT, and CLWB: Cache-line writeback/flush on x86 (deep dive)

• Not all CPUs support all instructions. Check CPUID bits:
  • CPU must perform a write to the cache line (store).
  • The cache line must be written back from caches to the memory controller/PMEM media (CLWB or CLFLUSH/CLFLUSHOPT).
  • Ordering must be enforced so that dependent updates persist in correct order (SFENCE between writebacks).
  • Provide a CPUID detection snippet for CLWB/CLFLUSHOPT support.
  • Produce a worked example showing a small persistent data structure using libpmem vs manual CLWB+SFENCE.
  • Show microbenchmarks or scripts to measure CLWB/CLFLUSH performance on your CPU.