[RFC] Tunable elision patch for siddhesh/tunables

[Siddhesh Poyarekar]

On Monday 05 October 2015 09:45 PM, Paul E. Murphy wrote:
> In continuing the glibc tunables discussion, I've made some
> additional patches which I think would help our work on the
> siddhesh/tunables branch.
> 
> I've split this into two patches:
> 
> * The first should enable tunables to initialize without
> calling malloc(), and prior to __environ being set.
> 
> * The second adds a common tunables initialization function
> for elision, and enables it for supported archs.
> 
> I have tested this on PPC64. I need help testing for
> supported s390 and x86 platforms.

I haven't done a thorough review, but the overall approach seems sane.
The only objection I have there is the new macro
TUNABLE_REGISTER_WITH_ENV.  You should be using the
COMPAT_TUNABLE_REGISTER instead and optionally pass it the envp.  I
don't currently have an opinion on whether a new environment variable
for elision is worth having, but that is a separate point that others
will likely have a strong opinion about.  I would only like it to be
separate from the core tunable infrastructure so that it does not
dictate which way the framework goes.

Thanks,
Siddhesh