摘要：Brendan Gregg, Joyent Performance issues can be complex and mysterious, providing little or no clue to their origin. In the absence of a starting point—or a methodology to provide one—performance issues are often analyzed randomly: guessing where the problem may be and then changing things until it goes away. While this can deliver results—if you guess correctly—it can also be time-consuming, disruptive, and may ultimately overlook certain issues. This article describes system-performance issues and the methodologies in use today for analyzing them, and it proposes a new methodology for approaching and solving a class of issues. Systems-performance analysis is complex because of the number of components in a typical system and their interactions. An environment may be composed of databases, Web servers, load balancers, and custom applications, all running upon operating systems—either bare-metal or virtual. And that's just the software. Hardware and firmware, including external storage systems and network infrastructure, add many more components to the environment, any of which is a potential source of issues. Each of these components may require its own field of expertise, and a company may not have staff knowledgeable about all the components in its environment.
