Re: how to let all others run

[John Fremlin <chief@bandits.org>]

"Richard B. Johnson" <root@chaos.analogic.com> writes:

> On 4 Apr 2001, John Fremlin wrote:
> > 
> > Hi Oliver!
> > 
> >  Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de> writes:
> > 
> > > is there a way to let all other runable tasks run until they block
> > > or return to user space, before the task wishing to do so is run
> > > again ?
> > 
> > Are you trying to do this in kernel or something? From userspace you
> > can use nice(2) then sched_yield(2), though I don't know if the linux
> > implementations will guarrantee anything.
> > 
> 
> I recommend using usleep(0) instead of sched_yield(). Last time I
> checked, sched_yield() seemed to spin and eat CPU cycles, usleep(0)
> always gives up the CPU.

What is wrong with this? sched_yield only yields to processes with
lower priority (hence suggestion to use nice(2)). Does sched_yield()
fail to yield in cases when a higher priority process wants to run? 
usleep() wastes time if no other such process is waiting, surely?

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