Eliminating a Processor Bottleneck

If you determine that you do have a processor bottleneck, consider some of these proposed solutions:

• Rule out a memory bottleneck that might be consuming the processor. Memory bottlenecks are far more common and severely degrade processor performance. For more information, see Chapter 12, "Detecting Memory Bottlenecks."

• Replace the application or try to fix it by using the performance optimizing tools in the Win32 Software Development Kit. Screen savers are notorious for monopolizing the processor, so monitor your screen saver executable.

• Upgrade your network or disk adapter cards. 8-bit cards use more processor time than 16-bit or 32-bit cards. The number of bits is the amount of data moved to memory from the adapter on each transfer, so 32-bit cards are the most efficient.

Look for cards that use bus-mastering direct memory access (DMA), not programmed I/O to move their data. Programmed I/O relies on processor instructions. In bus-mastering DMA, the disk controller managers the I/O bus and uses the DMA controller to manage DMA operation. This frees the processor for other uses.

• Increase the processor clock speed. Clock doubler and tripler processors multiply the processor clock speed while leaving the rest of the memory and I/O bus speeds alone. This will improve application response, but typically by less than the multiplier because applications do more than just use the processor.

• Increase the size of your secondary memory cache, especially if you've just added memory. When you add memory, the secondary cache must map the larger memory space, usually resulting in lower cache hit rates and more processor work retrieving data from the disk or network. Processor-bound programs are especially vulnerable because they are scattered more widely throughout memory after new memory is added.

The amount of secondary cache a system supports depends upon the design of the motherboard. Many motherboards support several secondary cache configurations (from 64K–512K or 256K–1MB). Increasing cache size usually requires removing the existing static ram (SRAM) chips, replacing them with new SRAM chips, and changing some jumpers. This is helpful when you have a working set that is larger than your current secondary cache.

• Upgrade to a faster processor or add another processor. The general rule is that a faster processor effectively improves performance when a single-threaded process is consuming the processor. Additional processors are recommended when you are running multiple processes or multithreaded processes.