Re: Database regression due to scheduler changes ?

Nick Piggin
2005-11-08T01:44:33Z

Martin J. Bligh wrote:

>>Im also considering adding balance on fork for ppc64, it seems like a
>>lot of people like to run stream like benchmarks and Im getting tired of
>>telling them to lock their threads down to cpus.
>
>
> Please don't screw up everything else just for stream. It's a silly
> frigging benchmark. There's very little real-world stuff that really
> needs balance on fork, as opposed to balance on clone, and it'll slow
> down everything else.
>

Long lived and memory intensive cloned or forked tasks will often
[but far from always :(] want to be put on another memory controller
from their siblings.

On workloads where there are lots of short lived ones (some bloated
java programs), the load balancer should normally detect this and
cut the balance-on-fork/clone.

Of course there are going to be cases where this fails. I haven't
seen significant slowdowns in tests, although I'm sure there would
be some at least small regressions. Have you seen any? Do you have
any tests in mind that might show a problem?

Thanks,
Nick

--
SUSE Labs, Novell Inc.

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