http://www.pcgamer.com/intel-and-microsoft-assess-performance-impact-of-meltdown-and-spectre-updates/

Both Microsoft and Intel have had some time to perform internal benchmarks after applying the latest Meltdown and Spectre updates, and both report seeing slowdowns to varying degrees. The extent depends on your specific hardware, with older systems being the hardest hit.

Starting with Intel, the chipmaker remains steadfast that most users have little to worry about, in terms of the performance impact.