7.3.1 Sequential Program
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7.3.1 Sequential Program

If the program runs fast enough on a single processor, and has no interactions with other processes, threads, or interrupt handlers, you should remove the synchronization primitives and spare yourself their overhead and complexity. Some years back, there were those who would argue that Moore's Law would eventually force all programs into this category. However, given the cessation in rate of CPU MIPS and clock-frequency growth in Intel CPUs since the year 2003, as can be seen in Figure increasing performance will increasingly require parallelism.7.4The debate as to whether this new trend will result in single chips with thousands of CPUs will not be settled soon, but given that Paul is typing this sentence on a dual-core laptop, the age of SMP does seem to be upon us. It is also important to note that Ethernet bandwidth is continuing to grow, as shown in Figure . This growth will motivate multithreaded servers in order to handle the communications load.

Figure: MIPS/Clock-Frequency Trend for Intel CPUs

Figure: Ethernet Bandwidth vs. Intel x86 CPU Performance

Please note that this does not mean that you should code each and every program in a multi-threaded manner. Again, if a program runs quickly enough on a single processor, spare yourself the overhead and complexity of SMP synchronization primitives. The simplicity of the hash-table lookup code in Figure underscores this point.7.5

Figure: Sequential-Program Hash Table Search

On the other hand, if you are not in this happy situation, read on!