Re: I like SCHED_4BSD

> > o Better interactivity -- No mouse jerkiness, no sluggish screen updates =
> when
> >   switching between virtual desktops, etc.
> >=20
> > o Better scheduling!  I'm serious here.  Watching top under SCHED_ULE, I'm
> >   seeing 10, 15, 20 seconds go by where ALL processes are sleeping.=20
> >   Processes seem to be spending inordinate amounts of time in the "kserel"
> >   state.  This, of course, doesn't happen with SCHED_4BSD.
> 
> That this observation may well be bogus, because you're trying to
> measure the scheduler using a tool that is itself run by the
> scheduler, so the process stats you see may not be representative of
> what is really happening on your system.

That point is taken, however, on my old SMP box _ULE adds an extra
~5000 seconds of wall clock time to a 'make buildworld -j8' compared
to _BSD 'make world -j8'.

I did some tests about 3 weeks ago using bind-dlz and postgresql-7.4.1
on this same machine trying libc_r and libkse using both schedulers.
ULE results with either thread library were dismal ~.33 that of
BSD: ULE gave about 17 authoritive lookups a second with BSD giving
about 50.  The KSE library only dropped the rate by about 2 lookups
per second on both schedulers which is essentially noise, but I had
expected an improvement.

Then there is the question about ULE and processor affinity which
I posed about a week ago which nobody has answered.  I'll pose it
here again:

------------------------
I thought I'd give ULE a spin again since according to Robert Watson
and David O'Brien's recents posts it appears that it might not to
slow down my system.

I noticed this oddity:

dnetc in order to utilize both CPUs forks a child which also
processes.  SCHED_4BSD seems to be aware that the second CPU is
idle and the child or parent (don't really care which) migrates to
the second CPU so that all CPU time is occupied on both CPUs.

SCHED_ULE doesn't seem to migrate processes to an idle CPU and as
a result one CPU in my system is 100% idle.

last pid:   677;  load averages:  2.06,  1.69,  0.89    up 0+00:09:57  09:22:29
40 processes:  3 running, 37 sleeping
CPU states:  0.0% user, 50.0% nice,  0.4% system,  0.4% interrupt, 49.2% idle
Mem: 25M Active, 25M Inact, 22M Wired, 56K Cache, 28M Buf, 111M Free
Swap: 512M Total, 512M Free

  PID USERNAME  PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
  624 ianf      139   20  1072K   884K RUN    0   4:00 48.44% 48.44% dnetc
  636 ianf      139   20  1072K   884K CPU0   0   3:26 48.44% 48.44% dnetc

Do processes have CPU afinity and is that afinity inherited by their
children?  Is this a wise thing to do since as demonstrated here
it is possible that all the CPU hogs may land up on 1 processor
thereby pessimising runtime?
------------------------

In my opinion ULE is not yet ready for prime-time.   Perhaps it
doesn't affect UP or is even more efficient with UP, but I thought
it was originally tabled as the new scheduler to make the SMP case
more efficient, which it certainly does not.

Ian

--
Ian Freislich