[RFC] Two versions of struct _Rb_tree_impl... or not?!

[Paolo Carlini]

Dhruv Matani wrote:

>What I think has happened is that the v3.3 and before has only a pointer to
>the actual root node, and newer versions have the actual node as part of the
>implementation structure. Hence, the difference in the size. Actually, the
>current method of having the actual node is better, because there is one
>poiner indirection less for every rb_tree operation.
>  
>
Yes, I learned the details of this myself yesterday. Thanks for the 
explanation, anyway.

>Anyways, the patch is ready, and there will not be much effort required from
>here on, so I guess the complexity issue should not come in. Consider that
>you have an array of say 100 maps, then the memory saved would be something
>like 400 bytes for x86 systems, which is quite a lot. We can save something
>like 400/32 cache lines with this simple optimization.
>  
>
Ok, let's proced like that: I will regtest the patch throughly during 
the next days,
on at least two different architectures. If everything goes well and 
nobody objects
to it, we'll apply it to mainline...

Paolo.