Re: [PATCH] jump_label: jump_label for boot options.

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Fri, 2011-12-02 at 13:45 +0100, Johannes Weiner wrote:
> On Fri, Dec 02, 2011 at 10:24:10AM +0100, Peter Zijlstra wrote:
> > On Fri, 2011-12-02 at 09:22 +0900, KAMEZAWA Hiroyuki wrote:
> > > 
> > > Yes, that's an idea. But we also have another stupid shadow swap accounting
> > > table.  This can be disabled at boot, too. 
> > 
> > Bah I thought it was just the page frame thing, hnaz any plans to kill
> > this swap array as well?
> 
> I haven't looked at the swap accounting at all yet, sorry.  But where
> did this discussion go all of a sudden? :-)
> 
> That array is not allocated at all when the memory controller is
> disabled at boot-time.
> 
> Rather, we have those mem_cgroup_disabled() conditionals everytime we
> enter the memory controller from the VM and the idea is to patch them
> out during boot, since you can not re-enable the thing anyway.

Yeah, but without those arrays you could.. this boot time switch really
is a wart and if you don't have the shadow page frame and shadow swap
accounting muck stuff you could runtime flip all this..

I've no objection to using jump_labels fwiw, we're looking to do the
same with the cpu controller for the nr_cgroups == 0 case. But boot time
stuff just doesn't make sense to me.