Re: [PATCH] idr: Document ida tree sections

[Kent Overstreet]

On Tue, Aug 13, 2013 at 06:44:28PM -0400, Tejun Heo wrote:
> Hello, Kent.
> 
> On Tue, Aug 13, 2013 at 03:27:59PM -0700, Kent Overstreet wrote:
> > It's only naturally a radix tree problem _if_ you require sparseness.
> 
> Well, it's not necessarily about requiring it but more about surviving
> it with some grace when things don't go as expected, which is an
> important characteristic for common library stuff.

The patch I posted should solve the high order allocations stuff, and
sparseness from cyclic allocations was already solved.

> > Otherwise, radix trees require pointer chasing, which we can avoid -
> > which saves us both the cost of chasing pointers (which is significant)
> > and the overhead of storing them.
> 
> Vast majority of which can be avoided with simple caching, right?

Whatever caching optimizations you do with a radix tree version I could
apply to this bitmap tree version, and my bitmap tree code is simpler
and _considerably_ faster than the existing code.
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