Fast path
Encyclopedia
Fast path is a term used in computer science
to describe a path with shorter
instruction path length
through a program compared to the 'normal' path. For a fast path to be effective it must handle the most commonly occurring tasks more efficiently than the 'normal' path, leaving the latter to handle uncommon cases, corner case
s, error handling, and other anomalies. Fast paths are a form of optimization
.
For example dedicated packet routing hardware used to build computer networks will often sport hardware dedicated to handling the most common kinds of packets, with other kinds, for example with control information or packets directed at the device itself instead of to be routed elsewhere, put on the metaphorical "slow path", in this example usually implemented by software running on the control processor.
Specific implementations of networking software architectures have been developed that leverage the concept of a fast path to maximize the performance of packet processing software. In these implementations, the networking stack is split into two layers and the lower layer, typically called the fast path, processes the majority of incoming packets outside the OS environment without incurring any of the OS overheads that degrade overall performance. Only those rare packets that require complex processing are forwarded to the OS networking stack, which performs the necessary management, signaling and control functions.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
to describe a path with shorter
instruction path length
Instruction path length
In computer performance, the instruction path length is the number of machine code instructions required to execute a section of a computer program. The total path length for the entire program could be deemed a measure of the algorithm's performance on a particular computer hardware...
through a program compared to the 'normal' path. For a fast path to be effective it must handle the most commonly occurring tasks more efficiently than the 'normal' path, leaving the latter to handle uncommon cases, corner case
Corner case
A corner case is a problem or situation that occurs only outside of normal operating parameters – specifically one that manifests itself when multiple environmental variables or conditions are simultaneously at extreme levels, even though each parameter is within the specified range for that...
s, error handling, and other anomalies. Fast paths are a form of optimization
Optimization (computer science)
In computer science, program optimization or software optimization is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources...
.
For example dedicated packet routing hardware used to build computer networks will often sport hardware dedicated to handling the most common kinds of packets, with other kinds, for example with control information or packets directed at the device itself instead of to be routed elsewhere, put on the metaphorical "slow path", in this example usually implemented by software running on the control processor.
Specific implementations of networking software architectures have been developed that leverage the concept of a fast path to maximize the performance of packet processing software. In these implementations, the networking stack is split into two layers and the lower layer, typically called the fast path, processes the majority of incoming packets outside the OS environment without incurring any of the OS overheads that degrade overall performance. Only those rare packets that require complex processing are forwarded to the OS networking stack, which performs the necessary management, signaling and control functions.