Threads and input/output in the synthesis kernal

The Synthesis operating system kernel combines several techniques to provide high performance, including kernel code synthesis, fine-grain scheduling, and optimistic synchronization. Kernel code synthesis reduces the execution path for frequently used kernel calls. Optimistic synchronization increases concurrency within the kernel. Their combination results in significant performance improvement over traditional operating system implementations. Using hardware and software emulating a SUN 3/160 running SUNOS, Synthesis achieves several times to several dozen times speedup for UNIX kernel calls and context switch times of 21 microseconds or faster.