Messages in this thread | | | Date | Wed, 25 Mar 2015 18:44:48 +0000 | From | Dietmar Eggemann <> | Subject | Re: [RFCv3 PATCH 45/48] sched: Skip cpu as lb src which has one task and capacity gte the dst cpu |
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On 24/03/15 15:27, Peter Zijlstra wrote: > On Wed, Feb 04, 2015 at 06:31:22PM +0000, Morten Rasmussen wrote: >> From: Dietmar Eggemann <dietmar.eggemann@arm.com> >> >> Skip cpu as a potential src (costliest) in case it has only one task >> running and its original capacity is greater than or equal to the >> original capacity of the dst cpu. > > Again, that's what, but is lacking a why. >
You're right, the 'why' is completely missing.
This is one of our heterogeneous (big.LITTLE) cpu related patches. We don't want to end up migrating this single task from a big to a little cpu, hence the use of capacity_orig_of(cpu). Our cpu topology makes sure that this rule is only active on DIE sd level.
We could replace the use of capacity_orig_of(cpu) w/ capacity_of(cpu) to take big.LITTLE and RT and/or IRQ work into consideration which then would effect the MC sd level too.
Will add the 'why' in the next version.
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