1. A system for improving performance of an operating system, comprising: a processor and memory; a subsystem that is implemented as a kernel mode driver and is configured to operate in a kernel mode of an operating system, the subsystem for receiving and processing requests for an operating system function from an operating system component, wherein the subsystem implements an application program interface of the operating system and complies with a portable operating system interface specification; and a kernel for receiving and processing function calls from the subsystem, the subsystem invoking the function calls to perform the requests, the function calls occurring in the kernel mode without causing a context switch from a user mode of the operating system.