Linked by Thom Holwerda on Tue 10th Jul 2007 21:57 UTC, submitted by maverick
The Linux kernel process scheduler, as you know it, has been completely ripped out and replaced with a completely new one called Completely Fair Scheduler. How fair it will be, remains to be seen. Here's what its original creator Ingo Molnar says: "80% Of CFS's design can be summed up in a single sentence: CFS basically models an 'ideal, precise multi-tasking CPU' on real hardware." Learn more about the new scheduler from the CFS design document.
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Member since:
2005-08-01
CFSv19 has many tunables in /proc/sys/kernel besides ns_granularity... Initially yes, it only had one like SD, but like I've previously posted, Ingo has been adding "smoothness" calculations and other "hand tuning" and also exposing more tunables. His "economy" based ideas (actually ideas of a college student) will only provide more heuristics ultimately leading to built-in unfairness. I don't think the economy based ideas made it into CFS.
A Completely Fair Scheduler shouldn't have heuristics if it should be truly fair. Initially both SD and CFS suffered from built in heuristics. SD has fixed those problems. CFS is still being tuned.
Perhaps these extra tunables are temporary until optimal values are found.. but it would seem that SD is better in this regard (inherently more fair by design).
Initially RSDL did have some problems, but they were fixed in (r)SDL -> SD. Part in thanks to Ingo and other developers giving Con some ideas.
btw, in CFSv19, most operations are O(1) time. Ingo's design document is out of date.
Edited 2007-07-11 01:54