[RFC] nptl: change default stack guard size of threads

[Jeff Law]

On 12/19/2017 06:06 AM, Florian Weimer wrote:
> On 12/19/2017 01:34 PM, James Greenhalgh wrote:
> 
>> Option 1: 64k guard pages for LP64 on AArch64.
> 
>> Option 2: 4k guard pages for LP64 for AArch64
> 
>> Our proposal then, having spoken things through with the Arm engineers
>> here, and taken in to consideration the opinions on this thread, is that
>> we move to two "blessed" configurations of the GCC support for AArch64.
> 
> Are there any Arm engineers who prefer Option 2, or is that just there
> to accommodate feedback on libc-alpha?
> 
> My main concern was the variance in configurations with Option 1
> (compared to Option 2).  To some extent, the variance with Option 1 is
> temporary.  If both Option 1 and 2 are offered, we have permanent
> variance.  From my point of view, that's worth that just going with
> Option 1.
> 
> So if this is some sort of consensus proposal, as opposed to actual
> technical requirements which favor Option 2 in some deployments, I think
> that's not a good idea, and we should go with Option 1 instead.
Ideally we set the guard size now and never ever decrease it.   I'd
really like to remove the option to make it a compile-time configurable
--param for GCC.  ie, it's baked into the port and never changes.

jeff