ULE/SCHED_SMP diff for 7.0, buildkernel & thanks.

[youshi10 at u.washington.edu]

On Tue, 17 Jul 2007, Jeff Roberson 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

I need to sync my kernel sources on my i386 desktop, but yeah I'll give it a round tonight.

-Garrett