[Bug 1647] Modular SuperCore Scheduler

bugzilla-daemon at rtems.org bugzilla-daemon at rtems.org
Fri Nov 12 02:41:16 UTC 2010


--- Comment #35 from Gedare <giddyup44 at yahoo.com> 2010-11-11 20:41:14 CST ---
(In reply to comment #34)
> > Why is this single time higher?  There was no change but we added about 50
> > instructions.
> > 
> > 21c23
> > < rtems_semaphore_obtain: not available -- caller blocks 700
> > ---
> > > rtems_semaphore_obtain: not available -- caller blocks 751
> I should have had more coffee before I wrote that. Let me try again.  The above
> is an example of a case which includes the worst case critical section in
> RTEMS. It appears that it is ~50 instructions longer.  You have mentioned some
> overhead due to the indirect calls and loss of some inlining but I am having
> trouble seeing that account for 50 instructions.  Help me out.

Inlining the scheduler and ready queue functions saves most of these
instructions, as I suspected.  The overheads probably are not observed on the
sparc since function calls are cheap (until the register windows are all used).

The latency of tm02 is tracking across multiple scheduler calls, so the
overheads accumulate.

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