SCHEDULE and high load situations

Don Lewis truckman at
Wed Aug 11 14:23:46 PDT 2004

On 11 Aug, Robert Watson wrote:
> On Wed, 11 Aug 2004, Martin Blapp wrote:
>> During load tests with both SCHED4BSD and SCHEDULE I found that the
>> latest SCHEDULE version cannot have a load over 2-3. I stress tested the
>> server really a lot, but about 500 processes did sleep and did not got
>> scheduled and only 2 of 500 were run and got about 50% of CPU time. 
>> Is this a known problem ? 
> I've found that for throughput oriented workloads, 4BSD substantially
> outperforms ULE, but I haven't tried it with Jeff's latest set of patches
> (committed a day or two ago).  You don't mention if your box is SMP, btw
> -- I've noticed some load balancing problems with ULE previously, but
> haven't checked if they were resolved.  Anecdotal opinion seems generally
> to be that interactivity is observably better with ULE than 4BSD, but that
> 4BSD appears to do a better job under load.

I've noticed in fork()/exec() intensive loads like buildworld and
building ports on a UP box that ULE favors a CPU-bound but niced process
like setiathome over the software build.  Even the longer c++ compile
steps seem to get less CPU time, than the niced CPU-bound process, at
least according to top.  Buildworld times with ULE on my Athlon XP box
are about 145 minutes with ULE and 82 minutes with 4BSD when competing
with setiathome.  Top shows setiathome consistently getting about 55% of
the CPU with ULE.  Without setiathome running, buildworld takes about 65

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