How well does Linux scale for SMP?
• (REG) Reasonably well. Kernel version 2.2 has much better scalability than version 2.0. People are running 4 processor Intel Xeon machines and 14 processor UltraSparc machines. Version 2.2 still has a global kernel lock, but this is often released quite quickly (for example, when the process blocks waiting for a resource and/or data), so the net result is that it is quite unlikely for two processors to compete for the global lock. Experiments with 14 processor UltraSparc machines shows that Linux scales well, indicating that the current locking strategy is not hurting us for these machines. Also consider that for parallel processing jobs, the kernel is not involved, so even Kernel v2.0 scaled well for these applications. When we talk about SMP scalability, we are referring to how many IO operations the kernel can perform at the same time. Unfortunately some hysterical NT supporters continue to spread FUD that Linux does not scale well on SMP. Efforts to insert a bit of truth have gen
