Re: sched_yield() makes OpenLDAP slow

[Nick Piggin]

Joseph Fannin wrote:

> On Thu, Aug 18, 2005 at 02:50:16AM +0200, Bernardo Innocenti wrote:
>
>
> > The relative timestamp reveals that slapd is spending 50ms
> > after yielding.  Meanwhile, GCC is probably being scheduled
> > for a whole quantum.
> >
> > Reading the man-page of sched_yield() it seems this isn't
> > the correct behavior:
> >
> >   Note: If the current process is the only process in the
> >   highest priority list at that time, this process will
> >   continue to run after a call to sched_yield.
>
>   The behavior of sched_yield changed for 2.6.  I suppose the man
> page didn't get updated.

We class the SCHED_OTHER policy as having a single priority, which
I believe is allowed (and even makes good sense, because dynamic
and even nice priorities aren't really well defined).

That also makes our sched_yield() behaviour correct.

AFAIKS, sched_yield should only really be used by realtime
applications that know exactly what they're doing.


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