Re: allow the load to grow upto its cpu_power (was Re: [Patch] don't kick ALB in the presence of pinned task)
From: Nick Piggin (nickpiggin_at_yahoo.com.au)
Date: 08/11/05
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To: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Date: Thu, 11 Aug 2005 13:09:10 +1000
On Tue, 2005-08-09 at 19:03 -0700, Siddha, Suresh B wrote:
> On Wed, Aug 10, 2005 at 10:27:44AM +1000, Nick Piggin wrote:
> > Yeah this makes sense. Thanks.
> >
> > I think we'll only need your first line change to fix this, though.
> >
> > Your second change will break situations where a single group is very
> > loaded, but it is in a domain with lots of cpu_power
> > (total_load <= total_power).
>
> In that case, we will move the excess load from that group to some
> other group which is below its capacity. Instead of bringing everyone
> to avg load, we make sure that everyone is at or below its cpu_power.
> This will minimize the movements between the nodes.
>
> For example, Let us assume sched groups node-0, node-1 each has
> 4*SCHED_LOAD_SCALE as its cpu_power.
>
> And with 6 tasks on node-0 and 0 on node-1, current load balance
> will move 3 tasks from node-0 to 1. But with my patch, it will move only
> 2 tasks to node-1. Is this what you are referring to as breakage?
>
No, I had thought it was possible to get into a situation where
one queue could be very loaded but not have anyone to pull from
it if total_load <= total_pwr.
I see that shouldn't happen though.
I have a variation on the 2nd part of your patch which I think
I would prefer. IMO it kind of generalises the current imbalance
calculation to handle this case rather than introducing a new
special case.
Untested as yet, but I'll queue it to send to Andrew after it
gets some testing - unless you have any objections that is.
Thanks,
Nick
-- SUSE Labs, Novell Inc.
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- Previous message: Jeff Garzik: "Re: [patch 14/16] net/tms380tr: replace direct assignment with set_current_state()"
- In reply to: Siddha, Suresh B: "Re: allow the load to grow upto its cpu_power (was Re: [Patch] don't kick ALB in the presence of pinned task)"
- Next in thread: Siddha, Suresh B: "Re: allow the load to grow upto its cpu_power (was Re: [Patch] don't kick ALB in the presence of pinned task)"
- Reply: Siddha, Suresh B: "Re: allow the load to grow upto its cpu_power (was Re: [Patch] don't kick ALB in the presence of pinned task)"
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