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CFQ In Linux Gets BFQ Characteristics
jones_supa writes: Paolo Valente from University of Modena has submitted a Linux kernel patchset which replaces CFQ (Completely Fair Queueing) I/O scheduler with the last version of BFQ (Budget Fair Queuing, a proportional-share scheduler). This patchset first brings CFQ back to its state at the time when BFQ was forked from CFQ. Paolo explains: "Basically, this reduces CFQ to its engine, by removing every heuristic and improvement that has nothing to do with any heuristic or improvement in BFQ, and every heuristic and improvement whose goal is achieved in a different way in BFQ. Then, the second part of the patchset starts by replacing CFQ's engine with BFQ's engine, and goes on by adding current BFQ improvements and extra heuristics." He provides a link to the thread in which it is agreed on this idea, and a direct link to the e-mail describing the steps.
Scheduling is an area many people don't really understand, as it is mostly behind the scenes.
It's also a very debated topic, as the optimal scheduling configuration often depends on what exactly a given machine is doing.
A server, for instance, may have many more processes running than a desktop, but they are largely the same type of processes. For this, a completely 'fair' type of scheduler may be the best choice.
A desktop however might be running far less processes at once, but they are vastly different. A mix of background processes and real-time applications, who's timing requirements vary between processes and possibly within a process at different times or situations. For this, a more heuristic based scheduler might be more appropriate, providing an overall 'more responsive' feeling experience.
This video shows the improvement
And why are they going thorough the trouble of removing improvements from CFQ?
CFQ was never very good, Lots of quirky behaviour, often being worse than the NOOP scheduler and sometimes stuffing up completely. This is a nice polite way of taking it out behind the barn and shooting it. The new one turns in massive improvements in read latency, respectable improvement in other loads, and little to no regression on any load, besides being thought through and 1,000,000 times better documented than the old steaming pile.
When all you have is a hammer, every problem starts to look like a thumb.
Been running PF-Kernel for a few years, which has a bunch of patches, including BFQ, ck patch set with BFS, Tux in ice, UKSM, and grayskys gcc kernel patch. I normally just use the PF Github repo
Love it. With BFQ, you no longer get system pauses on your desktop. I can listen to music or play a video, run a few vms, while a compiler runs in the background, and x-windows doesn't pause, typing doesn't pause, its how a system should act. Your system seems more fluid with no pausing.
PF-Kernel seems to be for Arch/Gentoo/Rpm based, but I've used it on Ubuntu systems. Pf-Kernel isn't the only one, there are other kernels out there that include more performance patches, Xanmod and Liquorix