Mach tuck significant in causing a tendency to dive, delta-winged aircraft with no foreplane or tailplane in the first case and, for example, the Lockheed P-38 in the second case. Alternatively, a particular design may have no significant tendency, for example the Fokker F28 Fellowship. As an aerofoil generating lift moves through the air, the air flowing over the top surface accelerates to a higher local speed than the air flowing over the bottom surface. When the aircraft speed reaches its critical Mach number the accelerated airflow locally reaches the speed of sound and creates a small shock wave, even though the
Mach (kernel) it would take just under 500μs. When Mach was first being seriously used in the 2.x versions, performance was slower than traditional monolithic operating systems, perhaps as much as 25%. This cost was not considered particularly worrying, however, because the system was also offering multi-processor support and easy portability. Many felt this was an expected and acceptable cost to pay. When Mach 3 attempted to move most of the operating system into user-space, the overhead became higher still: benchmarks between Mach and Ultrix on a MIPS R3000 showed a performance hit as great as 67% on some workloads. For example,