Oleg Goldshmidt wrote:
Yes, as in O(1). The implementation of the runqueue has changed in
CFS.
You are hinting that between the run queues nothing has changed. That
seem unlikely to me.
If so, how do the relative priorities happen?
I am not sure what you mean by "relative priorities". Do you mean,
"niceness"?
Yes. One of the things said about CFS was that with it things that
previously required real time priority now can run at nice -20 just as well.
That same text (I don't remember right now where I read it, nor who
wrote it) said that CFS fixed a nice anomality that used to exist with
O(1). Apparently, two adjacent nice levels are supposed to have a more
or less fixed CPU spread between them, no matter what the absolute nice
level is (the article suggested that if the system has just two
processes, one at nice level X and another at nice X+1, then the CPU
should be divided 45-55 between them). It was suggested that O(1) had
non-linear nice graph, due to the tricks played to make nice -20
approximate what it should do.
Only ready or running processes are scheduled - others don't even want
the CPU.
Being as it is that the load average on my system rarely goes above 4, I
can see why nobody is worried about O(log n).
Thanks,
Shachar
--
Shachar Shemesh
Lingnu Open Source Consulting Ltd.
http://www.lingnu.com
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