Re: allow the load to grow upto its cpu_power (was Re: [Patch] don't kick ALB in the presence of pinned task)

[Nick Piggin <nickpiggin@yahoo.com.au>]

Siddha, Suresh B wrote:
> On Thu, Aug 11, 2005 at 01:09:10PM +1000, Nick Piggin wrote:
> 
>>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.
> 
> 
> There is a difference between our changes. 
> 
> When the system is lightly loaded, my patch minimizes the number of 
> groups picking up that load. This will help in power savings for 
> example in the context of CMP. There are more changes required
> (user or kernel) for complete power savings, but this is a direction 
> towards that.
> 
> How about this patch?

Well, it is a departure from our current idea of balancing.
I would prefer to use my patch initially to fix the _bug_
you found, then we can think about changing policy for
power savings.

Main things I'm worried about:

Idle time regressions that pop up any time we put
restrictions on balancing.

This can tend to unbalance memory controllers (eg. on POWER5,
CMP Opteron) which can be a performance problem on those
systems.

Lastly, complexity in the calculation.

-- 
SUSE Labs, Novell Inc.

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