Subject: Re: [RFC PATCH v3 3/5] sched: nominate preferred wakeup cpu
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: vatsa@in.ibm.com
Cc: Gregory Haskins <gregory.haskins@gmail.com>,
       Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Suresh B Siddha <suresh.b.siddha@intel.com>,
       Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
       Ingo Molnar <mingo@elte.hu>, Dipankar Sarma <dipankar@in.ibm.com>,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
       Gautham R Shenoy <ego@in.ibm.com>, Andi Kleen <andi@firstfloor.org>,
       David Collier-Brown <davecb@sun.com>,
       Tim Connors <tconnors@astro.swin.edu.au>,
       Max Krasnyansky <maxk@qualcomm.com>
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Date: Tue, 11 Nov 2008 16:26:14 +0100
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On Tue, 2008-11-11 at 20:51 +0530, Srivatsa Vaddagiri wrote:
> On Tue, Nov 11, 2008 at 09:07:58AM -0500, Gregory Haskins wrote:
> > > Would it make sense to place the preferred_wakeup_cpu stuff in the
> > > root_domain structure we already have?
> > >   
> > 
> > From the description, this is exactly what the root-domains were created
> > to solve.
> > 
> > Vaidyanathan,  just declare your object in "struct root_domain" and
> > initialize it in init_rootdomain() in kernel/sched.c, and then access it
> > via rq->rd to take advantage of this infrastructure.  It will
> > automatically follow any partitioning that happens to be configured.
> 
> If I understand correctly, we may want to have more than one preferred
> cpu in a given sched domain, taking into account node topology i.e if a
> given sched domain encompasses two nodes, then we may like to designate
> 2 preferred wakeup_cpu's, one per node. If that is the case, then
> root_domain may not be of use here?

Agreed, in which case this sched_domain_attr stuff might work out better
- but I'm not sure I fully get that.. will stare at that a bit more.

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