Malloc improvements

[Anton Blanchard]

Hi Florian,

> > It's great to see the current focus on improving malloc. One thing
> > that would really help POWER is reducing the number of locks and
> > atomics in the fast path. Right now we have 3 in the malloc
> > fastpath and 2 in free. These add up.  
> 
> Does the hook variable read count as an atomic operation in this
> sense?

The read hook shouldn't be. The atomic issue I was referring to was
something we've been trying to solve for a while:

https://sourceware.org/ml/libc-alpha/2014-05/msg00118.html

Anton