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SubjectRe: [tip:perfcounters/core] x86: Add NMI types for kmap_atomic
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On Mon, 2009-06-15 at 20:42 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Mon, 2009-06-15 at 20:25 +0200, Ingo Molnar wrote:
> > > * Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > > but ... look at the APIs i propose above. We dont need _any_
> > > 'types'.
> > >
> > > That type enumeration is basically an open-coded allocator. If we do
> > > a _real_ allocator (a balanced stack of atomic kmaps) we dont need
> > > any of those indices, and all the potential for mismatch goes away
> > > as well - a stack nests trivially with IRQ and NMI and arbitrary
> > > other contexts.
> >
> > You want types because:
> > - they encode the intent, and can be verified
> > - they help keep track of the max nesting depth
> >
> > In the proposed implementation all type code basically falls away
> > no ! CONFIG_DEBUG_VM, but is kept around for robustness.
>
> But much of the fragility of the types (and their clumsiness - for
> example in highpte ops we have to know at which level of the
> pagetables we are, and use the right kind of index) is _precisely_
> because we have the types ...

How will you manage the max depth?



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