You're right that early microkernels (Mach) were pretty awfully slow. But that was really more the early 90's. Even before 2000 there were new systems that we

You're right that early microkernels (Mach) were pretty awfully slow. But that was really more the early 90's. Even before 2000 there were new systems that were already much, much faster than Mach. If you read the article, you'll see several references to papers that show microkernel performance on par with or better than traditional monolithic Unix systems. For example, "EROS: a fast capability system" by Shapiro, Smith, and Farber, in SOSP 1999. http://dl.acm.org/citation.cfm?doid=319151.319163 http://dl.acm.org/citation.cfm?doid=319151.319163