最近在查 top 指令所顯示資訊的含意。主要是針對1, 5, 15 minutes load average 的解釋。load average看字面很容易解釋,但背後所表示的含意為何?以及該如何解讀這些數字? 找了一會,居然沒找到一個明瞭、或簡單易懂的說明。忽然想到之前在 Building Scalable Web Sites (台灣翻譯為 聚沙成塔~建置逐層擴充的Web2.0 服務 )這本書中,於Bottlenecks章節內,有提到關於CPU部分。翻了一下書,果然有說明…節錄做個記錄… The load average statistic is a very good quick indicator of the general state of the machine. The three figures shown represent the load average over the last 1, 5, and 15 minutes. The load average is calculated by counting the number of threads in the running or runnable states at any one time. The running state means that the process is currently executing on a processor, while the runnable state means the process is ready to run and is waiting for a processor time slice. The load average is averaged out using samples of the queue length taken every five seconds (on Linux), averaged, and damped over the three time periods. The load average is never an indication of how many processes are trying to run at any one moment. A load average o...