Re: [Slightly off topic] A question about R/B trees.

[Maxim Levitsky]

Pekka Enberg wrote:
> Hi Andi,
>
> On Sat, Oct 18, 2008 at 10:53 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> > The problem with hash tables is that if they're big enough
> > or if the rest of the workload is memory intensive
> > each hit will be a cache miss. And you can do a lot of branch
> > mispredicts in the time of a single cache miss.
> >
> > In general trees can be much better for cache usage, although
> > it's generally better to use some tree that has nodes near
> > the cache line size. Binary trees like RB are too small for that.
>
> Right, but even for binary trees, you can get some of the benefits by
> packing all the nodes in a slab cache of their own. That way many of
> the neighboring nodes will share the same cache line if you're
> allocating memory for the nodes in a top-down order. Of course, you
> lose the benefits if the tree is updated a lot because you're back to
> worst case allocation again.
>
>                        Pekka

Thank you very much.

Best regards,
	Maxim Levitsky
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