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SubjectRe: 2.4.17 absurd number of context switches
On Fri, 28 Dec 2001, Alan Cox wrote:

> > > The scheduler is _good_ at the three process case. Run some straces it looks
> > > more like postgres is doing wacky yield based locks.
> >
> > The scheduler that Linus merged in 2.5.2-pre3 will solve the problem.
> Looking at the postgres traces here it wont make any difference at all. Not
> one iota. If I am reading it right I have processes each going
> yield, yield, yield... so the kernel does just that (and indeed posix
> semantics require that behaviour).

task A old the lock , counter = 2
task B counter = 5 and task C counter = 4 are woke up
try to look at a switch dump.
the scheduler will spend 3 entire time slices switching between B and C
before A will get back the CPU and will free the lock.

- Davide

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