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Subject: Re: [RFT][PATCH] sched, cgroup: Optimize load_balance_fair()
From: Peter Zijlstra <peterz@infradead.org>
To: Paul Turner <pjt@google.com>
Cc: Nikhil Rao <ncrao@google.com>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
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Date: Wed, 13 Jul 2011 23:01:03 +0200
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On Wed, 2011-07-13 at 10:13 -0700, Paul Turner wrote:
> > +static void update_h_load(long cpu)
> > +{
> > +       walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
> > +}
> 
> With a list_for_each_entry_reverse_rcu() this could also only operate
> on the local hierarchy and avoid the tg tree walk. 

Ah, sadly that primitive cannot exist, rcu list primitives only keeps
the fwd link.

Although I guess we could 'fix' that.