Re: [PATCH RFC 1/4] lib/radix: add universal radix_tree_fill_range

[Konstantin Khlebnikov]

On Wed, Aug 31, 2016 at 7:36 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> On Wed, Aug 31, 2016 at 7:57 AM, Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> wrote:
>> I'm not at all against the idea of having a tree which supports ranges, except that we already have one; the interval tree.  Did you investigate using the interval tree for your use case?
>
> I am continuing to investigate, but that is orthogonal to whether
> Konstantin's changes are an improvement for the radix implementation.
> Hmm, would we have ended up with two data-structures if a range-based
> radix was available?

Interval tree is a augmented rb-tree. AFAIK it doesn't support RCU lookup
without special dances with sequential counters - some branches disappears
from RCU readers during rebalance.

>
> The benefits I see is that it simplifies insertion as it no longer
> needs to explicitly manage the order of the entries, and, iiuc, let's
> the user skip the sibling-to-head conversion when it is not needed
> which simplifies lookups.