Re: [PATCH] memcg: remove unneeded preempt_disable

[Christoph Lameter]

On Thu, 25 Aug 2011, Peter Zijlstra wrote:

> On Thu, 2011-08-18 at 14:40 -0700, Andrew Morton wrote:
> >
> > I think I'll apply it, as the call frequency is low (correct?) and the
> > problem will correct itself as other architectures implement their
> > atomic this_cpu_foo() operations.
>
> Which leads me to wonder, can anything but x86 implement that this_cpu_*
> muck? I doubt any of the risk chips can actually do all this.
> Maybe Itanic, but then that seems to be dying fast.

The cpu needs to have an RMW instruction that does something to a
variable relative to a register that points to the per cpu base.

Thats generally possible. The problem is how expensive the RMW is going to
be.

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