Web Performance Tuning

Bus

A bus is a set of parallel wires (usually 32, 64, 128, or 256 wires, plus error and protocol handling wires) embedded in a board forming the backbone of the computer. Other components, including CPU, disk, memory, and network cards, are connected to each other by their shared bus.

There may be more than one bus in a computer. PCs may have only one bus connecting everything. Server hardware, however, typically has at least two separate busses: a high-speed bus for connecting memory to the CPU, and a slower bus for connecting I/O to the CPU. System busses lag CPU speed by a large margin, meaning that CPUs spend a great many cycles simply sitting and waiting for the bus to catch up. On the other hand, busses are usually faster than network connections. As already mentioned, this has been changing recently. Fast Ethernet, for example, runs at 100Mbps, which is more than ISA or EISA busses can handle. Gigabit Ethernet runs at 1000Mbps, which is even more of a challenge. At gigabit rates, the server bus and CPU generally become the bottleneck, especially if the CPU is trying to do database access or run CGI applications at the same time.

While a throughput of 1056Mbps from a 32-bit 33MHz PCI bus is technically possible, your true throughput will be far lower because of contention, network packet overhead, OS implementation, and many other issues. 10Mbps is good TCP/IP throughput for a PC. A Sun Ultra 1 should get much better than 40Mbps of TCP/IP throughput. (The advertised rates you ...