The document discusses performance differences between Linux and Solaris (SmartOS). It begins by providing an example of a Perl program that runs 14% slower on one system versus the other. This example is used to explore potential reasons for performance differences between operating systems. The document then categorizes differences into major ("big") differences, such as kernel features, and minor ("small") differences, such as tunable parameters. Several major performance-related features of both Linux and Solaris are highlighted. The document cautions against a "Not Invented Here" viewpoint and suggests areas where each system could potentially learn from the other to improve performance.