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:2005-07-24
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Linus was simply complaining because more people were willing to give CFS a try and post benchmark results (mostly highlighting problems with fairness compared to SD), while SD benchmark results were much less publicized. Probably because numbers weren't needed, it simply felt "smoother".. CK did try calling for more people to post benchmarks, but by then SD was basically wrote off from getting into mainline.
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That's... unconvincing.
I've not followed all of this closely. But the major thwarting factor that I have noted is the scenario where one process, which looks like a processor hogging server, does its very sensitive work on behalf of a very much interactive client. The premiere example being X.
Are you saying that after all this we are no closer to solving this problem? Renice X to -10 has been the "solution" to this particular problem for as long as I have been aware of it. Which means back in the 90's.
Excuse me for a moment while I throw myself onto my sword. ;-)
Member since:2005-08-01
What i'm saying is:
In the past, a renice of X to -10 was recommended by CK for RSDL to overcome X not updating enough (low FPS).
At the time Ingo and Linus were saying that we shouldn't have to renicie to -10. I agree.
Since then, SD has been fixed and X at priority 0 is perfectly fine. Renicing to -10 doesn't really help all that much anymore.
Since then, CFS has come out to fix the old RDSL problem, but it still benefits from renicing X to -10 more so than SD. Sure, it can be run at priority 0 too, but with less "smoothness" i.e. FPS.
The link you brought up was true for RSDL, but is no longer the case. I would say the opposite is true now. CFS should be fixed (and it is being actively developed). While SD has been put on the back burners because of a lack of interest (due to the negative reaction to CK and RSDL).
Member since:
2005-08-01
That argument was for RSDL v.31 when renicing X to -10 helped out Xorg a lot in gaining more CPU time for itself (to improve user experience under load).
Now realize that Ingo also now supports renicing X to -10. He even made a patch for the kernel to do it automatically (i'm current using that patch with CFSv19).
It's precisely that kind of doublespeak that got CK upset. me too. Since then renicing to -10 isn't required, but still recommended (more so for CFS than SD in their current versions).
I did actual benchmarks for each version of SD vs CFS under the same conditions. All priorities at default 0... and SD won.
Linus was simply complaining because more people were willing to give CFS a try and post benchmark results (mostly highlighting problems with fairness compared to SD), while SD benchmark results were much less publicized. Probably because numbers weren't needed, it simply felt "smoother".. CK did try calling for more people to post benchmarks, but by then SD was basically wrote off from getting into mainline.
Edited 2007-07-11 01:06