Linux: Turning Relayfs into an API

A recent discussion and series of patches on theLinux Kernel mailing list looked at removingrelayfs [story], moving its functionality into an API using sysfs. Paul Mundt offered the patches summarizing, "this is a small patch set for getting rid of relayfs, and moving the core of its functionality to kernel/relay.c. The API is kept consistent for everything but the relayfs-specific bits, meaning people will have to use other file systems to implement relay channel buffers." The thread offers more explanation as to the benefits of the change, with quite a number of people supporting the patches.

Relayfs is described as "a bunch of per-cpu kernel buffers that can be efficiently written into from kernel code. These buffers are represented as files which can be mmap'ed and directly read from in user space. The purpose of this setup is to provide the simplest possible mechanism allowing potentially large amounts of data to be logged in the kernel and 'relayed' to user space." It was originally merged into Andrew Morton [interview]'s -mm tree in January of 2005 [story], and finally made it into the mainline kernel with the release of 2.6.14.