Re: boot-time slowdown for measure_migration_cost

[Chuck Ebbert]

In-Reply-To: <20060130200026.GA5081@xxxxxxxxxxxxxxxxxxxxxxxxx>

On Mon, 30 Jan 2006, Tony Luck wrote:

> Might it be wise to see whether the 2% variation that I saw can be
> repeated on some other architecture?  Bjorn's initial post was just
> questioning whether we need to spend this much time during boot to acquire
> this data.  Now we have *one* data point that on an ia64 with four cpus
> with 9MB cache in a single domain that we can speed the calculation by
> a factor of three with only a 2% loss of accuracy.  Can someone else try
> this patch and post the before/after values for migration_cost from dmesg?

Before:

messages.1:Jan 24 01:19:45 d2 kernel: [    6.377117] migration_cost=9352
messages.1:Jan 27 21:07:55 d2 kernel: [    6.384871] migration_cost=9329
messages.1:Jan 28 11:00:32 d2 kernel: [    6.384215] migration_cost=9338
messages.1:Jan 28 12:55:03 d2 kernel: [    6.389189] migration_cost=9364


After:

messages:Jan 31 07:55:07 d2 kernel: [    1.859359] migration_cost=9274


This was on a dual PII Xeon with 2MB L2 cache.  About 3.5x as fast and
only 1% change.

Maybe the default could be to run the quick test with an option to run the
more-accurate one?

-- 
Chuck
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