Re: Segments

On Thu, 16 Jan 2025 18:12:46 +0000, Thomas Koenig wrote:

Waldek Hebisch <antispam@fricas.org> schrieb:

David Brown <david.brown@hesbynett.no> wrote:

>

>

Which at first glance look
great.  But once one realize how small are stacks in modern
systems (compared to whole memory), this no longer looks good.

>
Stacks are small because OS people make them small, not because of
a valid technical reason that has ever been explained to me.
"To avoid infinite recursion" is not a valid reason, IMHO.

Algol 60 only had stack allocation for dynamically sized arrays,
so stacks had to be as big as the data are.

Basically, to use VLA one needs rather small bound on maximal
size of array.  Given such bound always allocating maximal
size is simpler.  Without _small_ bound on size heap is
safer, as it is desined to handle also big allocations.

>
Allocating data on the stack promotes cache locality, which can
increase performance by quite a lot.

If/when HW can track deallocating stack storage; the core
does not have to write back modified lines to memory at cache
line replacement. {{Look, once the SP moves out of that part of
the stack, nobody is allowed to dereference it anymore, so,
nobody cares about the value in those containers.}}