On Fri, 2010-12-17 at 17:09 +0200, Avi Kivity wrote:
Task X wants control of when runnable task Y gets the cpu. Task X
clearly wants to be the scheduler. This isn't about _yielding_ diddly
spit, it's about individual tasks wanting to make scheduling decisions,
so calling it a yield is high grade horse-pookey. You're trying to give
the scheduler a hint, the stronger that hint, the happier you'll be.
I can see the problem, and I'm not trying to be Mr. Negative here, I'm
only trying to point out problems I see with what's been proposed.
If the yielding task had a concrete fee he could pay, that would be
fine, but he does not.
If he did have something, how often do you think it should be possible
for task X to bribe the scheduler into selecting task Y? Will his
pockets be deep enough to actually solve the problem? Once he's
yielded, he's out of the picture for a while if he really gave anything
up. What happens to donated entitlement when the recipient goes to
sleep? If you try to give it back, what happens if the donor exited?
Where did the entitlement come from if task A running alone on cpu A
tosses some entitlement over the fence to his pal task B on cpu B.. and
keeps on trucking on cpu A? Where does that leave task C, B's
competition?
Nothing between the lines about it. There are N individual engines,
coupled via load balancing.
-Mike
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