malloc(3) (hopefully) set for 7.0

[Jason Evans]

Ivan Voras wrote:
> [...] I'd really like if you could manage to implement
> those ideas before 7.0, and here's why:
> 
> - The standard for new servers here is 4 cores (in various socket
> arrangements), and we're not at all high-tech. This is likely to go up.
> - If you include hyperthreading, even all *desktops* are SMPs! In short,
> even including desktops, I haven't installed a UP kernel in about a year.
> - It's too long to wait for 8.0 for something as important as this.

I already implemented features in malloc that greatly _reduce_ 
malloc-related contention, so I don't think it is necessary to rush 
further enhancements that would nearly _eliminate_ contention.  We are 
already in pretty good shape.  Also, of the enhancements I have in mind, 
those with highest (predicted) payoff are self-contained enough that 
backporting to RELENG_7 might be feasible.

Jason