Computer Abstractions and Techno

1.9 Real Stuff: Benchmarking the Intel Core i7

这一节是讲性能测试。如果要提升性能，就要加速大概率事件：

As we noted above, to make the common case fast, you first need to know accurately which case is common, so benchmarks play a critical role in computer architecture.

那么，这就涉及到两个概念：

workload A set of programs run on a computer that is either the actual collection of applications run by a user or constructed from real programs to approximate such a mix. A typical workload specifies both the programs and the relative frequencies.

benchmark A program selected for use in comparing computer performance.

行业建立了称之为SPEC（System Performance Evaluation Cooperative）的组织，进行性能和功耗的测试。

其中，性能测试的结果体现为SEPCratio：

SPECratio, which has the advantage that bigger numeric results indicate faster performance. That is, the SPECratio is the inverse of execution time. A CINT2006 or CFP2006 summary measurement is obtained by taking the geometric mean of the SPECratios.

案例：

公式如下：

采用几何平均值的好处是，针对不同的芯片，在同一个测试标准下，可以直接相除得到相对性能：

When comparing two computers using SPECratios, apply the geometric mean so that it gives the same relative answer no matter what computer is used to normalize the results. If we averaged the normalized execution time values with an arithmetic mean, the results would vary depending on the computer we choose as the reference.

此外，功耗测试的结果体现为SPECpower：

SPEC added a benchmark to measure power. It reports power consumption of servers at different workload levels, divided into 10% increments, over a period of time.

案例：

公式如下：