![]() ![]() Some physical components have been left out, such as hardware caches (eg, MMU TLB/TSB, CPU). Request resources can be defined as queueing systems, which can queue and then service requests. Both types can become a system bottleneck. Some components are two types of resources: storage devices are a service request resource (I/O) and also a capacity resource (population). CPUs: sockets, cores, hardware threads (virtual CPUs).To begin with, you need a list of resources to iterate through. The monitoring tool was reporting five minute averages, during which CPU utilization hit 100% for seconds at a time. I had an example where a customer had problems with CPU saturation (latency) even though their monitoring tools showed CPU utilization was never higher than 80%. Does Low Utilization Mean No Saturation?Ī burst of high utilization can cause saturation and performance issues, even though utilization is low when averaged over a long interval. This includes operations that fail and are retried, and devices from a pool of redundant devices that fail. eg, "this network interface has had fifty late collisions".Įrrors should be investigated because they can degrade performance, and may not be immediately noticed when the failure mode is recoverable. eg, "the CPUs have an average run queue length of four". eg, "one disk is running at 90% utilization". utilization: as a percent over a time interval.The metrics are usually expressed in the following terms: There is another definition where utilization describes the proportion of a resource that is used, and so 100% utilization means no more work can be accepted, unlike with the "busy" definition above. It can be useful to consider some software resources as well, or software imposed limits (resource controls), and see which metrics are possible. saturation: the degree to which the resource has extra work which it can't service, often queued.utilization: the average time that the resource was busy servicing work.resource: all physical server functional components (CPUs, disks, busses.It's intended to be used early in a performance investigation, to identify systemic bottlenecks. The USE Method can be summarized as: For every resource, check utilization, saturation, and errors. There are many problem types it doesn't solve, which will require other methods and longer time spans. It should be thought of as a tool, one that is part of larger toolbox of methodologies. I find it solves about 80% of server issues with 5% of the effort, and, as I will demonstrate, it can be applied to systems other than servers. The USE Method is based on three metric types and a strategy for approaching a complex system. The USE Method has been used successfully countless times in different enterprise environments, classroom environments (as a learning tool), and more recently in cloud computing environments. Like an emergency checklist in a flight manual, it is intended to be simple, straightforward, complete, and fast. I developed the USE Method to teach others how to solve common performance issues quickly, without overlooking important areas. Performance monitoring products can make the USE method easier to follow by providing its metrics via an easy-to-use interface.Ī serious performance issue arises, and you suspect it's caused by the server. There is also the Rosetta Stone of Performance Checklists, automatically generated from some of these. You can customize these for your environment, adding additional tools that your site uses. The resulting USE Method-derived checklists for different operating systems are listed on the left navigation panel ( Linux, Solaris, etc). ![]() ![]() It begins by posing questions, and then seeks answers, instead of beginning with given metrics (partial answers) and trying to work backwards. It directs the construction of a checklist, which for server analysis can be used for quickly identifying resource bottlenecks or errors. The Utilization Saturation and Errors (USE) Method is a methodology for analyzing the performance of any system. ![]()
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