Re: ULE/SCHED_SMP diff for 7.0, buildkernel & thanks.

On 7/17/07, Jeff Roberson <jroberson_at_chesapeake.net> wrote:
> With regards to buildkernel times;  I do not want to sacrafice performance
> on other benchmarks to improve buildkernel.  The problem is that 4BSD is
> as agressive as possible at scheduling work on idle cores.  This behavior
> that helps one buildworld hurts on other, in my opinion, more important
> benchmarks.
>
> For example: http://people.freebsd.org/~jeff/sysbench.png
>
> ULE is 33% faster than SCHED_4BSD at this mysql test.  This is a direct
> result of prefering to idle to make more efficient scheduling decisions.
> ULE is also faster at various networking benchmarks for similar reasons.
>
> I also believe that while the real time may be slower on buildworld the
> system and user time will be smaller by a degree greater than the delta in
> real time.  This means that while you're building packages you have a
> little more cpu time leftover to handle other tasks.  Furthermore, as the
> number of cores goes up things start to tip in favor of ULE although this
> is somewhat because it's harder for even 4BSD to keep them busy due to
> disk bandwidth.
>
> Thanks everyone for testing.  Can someone confirm that they have tested
> with x86 rather than amd64?  I will probably commit later today.
>
> Thanks,
> Jeff
>
> On Tue, 17 Jul 2007, Claus Guttesen wrote:
>
> >> > sched_ule:
> >> >
> >> > -j 3 buildkernel: 13:23
> >> > -j 4 buildkernel: 12:38
> >> > -j 5 buildkernel: 12:41
> >> > -j 6 buildkernel: 12:47
> >> >
> >> > sched_4bsd:
> >> > -j 3 buildkernel: 11:43
> >> > -j 4 buildkernel: 12:02
> >> >
> >> > So sched_ule seems to handle more processes slightly better than 4bsd
> >> > albeit it does it slower. ule's sweet spot is -j 4 and 4bsd is -j 3.
> >> >
> >>
> >> 4bsd vs ULE
> >>
> >> -j 3 buildkernel: 11:43 vs -j 3 buildkernel: 13:23
> >>
> >> -j 4 buildkernel: 12:02 vs -j 4 buildkernel: 12:38
> >>
> >>
> >> ULE is always slower?
> >
> > In my case yes.
> >
> > --
> > regards
> > Claus
> >
> > When lenity and cruelty play for a kingdom,
> > the gentlest gamester is the soonest winner.
> >
> > Shakespeare
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Patch applied to my i386 CURRENT system with sources checked out
today.  Everything compiled cleanly and system has been running well
since then.