The Really Fair Scheduler

derrida writes "During the many threads discussing Ingo Molnar's recently merged Completely Fair Scheduler, Roman Zippel has repeatedly questioned the complexity of the new process scheduler. In a recent posting to the Linux Kernel mailing list he offered a simpler scheduler named the 'Really Fair Scheduler' saying, 'As I already tried to explain previously CFS has a considerable algorithmic and computational complexity. This patch should now make it clearer, why I could so easily skip over Ingo's long explanation of all the tricks CFS uses to keep the computational overhead low — I simply don't need them.'"

Comments

Smarter write throttling is the answer

[Spoke]

It's fairly well known that large writes to the filesystem can cause huge read delays.

This seems to be aggravated by a number of conditions listed in the links posted by the parent post, but it's also aggravated when using ext3 and ordered data journaling as well (which is the default on most systems).

There is some work being done to reduce the huge latency in reads that can occur during heavy write loads with the "per device dirty throttling" patchset. Initial results look very promising.

LWN article: Smarter write throttling
per device dirty throttling -v8

This patch set seems to hold a lot of promise in being able to fix this problem, but I'm not sure what the latest status is or what kernel it will make it into. It could make it into 2.6.24 at the earliest.