Chapter 12, Problem 12.23HW

Program Plan Intro

I/O Multiplexing:

• The idea of I/O multiplexing is to use “select” function to ask kernel to suspend process.
• It returns control to application only after one or more I/O events had occurred.
• It denotes waiting for a set of descriptors that is ready for reading.
• The “select” function would manipulate sets of type “fd_set”, that denotes descriptor sets.
• It takes two inputs: a descriptor set called “read set” and cardinality of read set.
• It blocks until at least one descriptor in read set is ready for reading.
• A descriptor “k” is ready for reading if and only if a request to read 1 byte from that descriptor would not block.
• The “fd_set” is been modified that points to argument “fdset” to indicate subset of read set called “ready set”.
• The value returned by function indicates cardinality of ready set.