"After posting some benchmarks involving cfs, I got some feedback, so I decided to do a follow-up that'll hopefully fill in the gaps many people wanted to see filled," Rob Hussey began. He added, "this time around I've done the benchmarks against 2.6.21, 2.6.22-ck1, and 2.6.23-rc6-cfs-devel (latest git as of 12 hours ago)." Rob briefly summarized, "the only analysis I'll offer is that both sd and cfs are improvements, and I'm glad that there is a lot of work being done in this area of linux development. Much respect to Con Kolivas, Ingo Molnar, and Roman Zippel, as well all the others who have contributed."

Referring to a chart in which the blue line represented the CFS process scheduler, and the green line represented the SD "staircase" process scheduler, Ingo Molnar noted, "heh - am i the only one impressed by the consistency of the blue line in this graph? :-) [ and the green line looks a bit like a .. staircase? ]" He acknowledged some slowdown in CFS compared to SD in one of the benchmarks, "-ck1 is 0.8% faster in this particular test." Ingo then explained, "many things happened between 2.6.22-ck1 and 2.6.23-cfs-devel that could affect performance of this test. My initial guess would be sched_clock() overhead." In further testing he applied a low-res-sched-clock that resulted in better performance for CFS leading him to conclude, "the performance difference between -ck and -cfs-devel seems to be mostly down to the more precise (but slower) sched_clock() introduced in v2.6.23 and to the startup penalty of freshly created tasks." When asked if the low-res-sched-clock was likely to be merged, Ingo replied:

"I don't think so - we want precise/accurate scheduling before performance. (otherwise tasks working off the timer tick could steal away cycles without being accounted for them fairly, and could starve out all other tasks.) Unless the difference was really huge in real life - but it isn't."

"Looking at these graphs (and the fixed one from your second email), it sure looks a lot like CFS is doing at *least* as well as the old scheduler in every single test, and doing much better in most of them (in addition it's much more consistent between runs)," Kyle Moffett noted regarding recent benchmarks run against the Completely Fair Scheduler by Rob Hussey. Kyle continued:

"This seems to jive with all the other benchmarks and overall empirical testing that everyone has been doing. Overall I have to say a job well done for Ingo, Peter, Con, and all the other major contributors to this impressive endeavor."