Re: ULE/SCHED_SMP diff for 7.0

From: Dmitry Morozovsky <marck_at_rinet.ru>
Date: Thu, 19 Jul 2007 12:16:32 +0400 (MSD)
On Wed, 18 Jul 2007, Jeff Roberson wrote:

JR> > Works for me with MSI S420 lapton (core2duo T2400) on fresh -CURRENT/i386
JR> > CPU: Genuine Intel(R) CPU           T2400  _at_ 1.83GHz (1833.41-MHz
JR> > 686-class CPU)
JR> > 
JR> > However, make -j3 buildworld buildkernel (trimmed GENERIC) time degraded
JR> > by 7%:
JR> > 
JR> > +------------------------------------------------------------------------------+
JR> >    N           Min           Max        Median           Avg        Stddev
JR> > x   5         36.33         36.77         36.45        36.486
JR> > +   5         38.87         39.23         39.03        39.042
JR> > Difference at 95.0% confidence
JR> >        2.556 +/- 0.216322
JR> >        7.00543% +/- 0.59289%
JR> >        (Student's t, pooled s = 0.148324)
JR> > 
JR> > before = kernel with SCHED_4BSD, after = SCHED_ULE with your patchset.
JR> > Both
JR> > are without WITNESS/INVARIANTS.
JR> 
JR> Hi Dmitry,
JR> 
JR> Can you test with http://people.freebsd.org/~jeff/sched_ule.c?  I believe
JR> this will somewhat improve the situation with buildkernel.  I have tested
JR> with my own core2duo laptop.  The first run after reboot is now about 7%
JR> faster than before.  Subsequent runs are not improved as much.  Only 2-3%.
JR> You can also try tuning sysctl kern.sched.steal_thresh down as low as 1 to
JR> see how much this may help.  Unfortunately lower values tend to really hurt
JR> other tests.


Well, I'm a bit puzzled: with new sched_ule.c system+user time slightly 
decreases (within one minute), while real time goes up from 39 to 44 minutes!  
And most of the time I see 10-50% of idle in top.

Any hints?

Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck_at_rinet.ru ***
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Received on Thu Jul 19 2007 - 06:16:43 UTC

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