Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

[Balbir Singh]

* Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> [2010-11-19 12:49:36]:

> On Fri, 2010-11-19 at 00:43 +0100, Samuel Thibault wrote:
> > What overhead? The implementation of cgroups is actually already
> > hierarchical. 
> 
> It must be nice to be that ignorant ;-) Speaking for the scheduler
> cgroup controller (that being the only one I actually know), most all
> the load-balance operations are O(n) in the number of active cgroups,
> and a lot of the cpu local schedule operations are O(d) where d is the
> depth of the cgroup tree.
>
> [ and that's with the .38 targeted code, current mainline is O(n ln(n))
> for load balancing and truly sucks on multi-socket ]
>

I can say that for memory, with hierarchies we account all the way up,
which can be a visible overhead, depending on how often you fault.
 

-- 
	Three Cheers,
	Balbir
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