Bug#934080: [libc6] Significant degradation in the memory effectivity of the memory allocator

[Florian Weimer <fweimer@redhat.com>]

* Roman Savochenko:

> Initial condition of the problem representing is a program in the
> single source code, built on-and for Debian 7, 8, 9, 10 with a result
> in the Live disks.

I think glibc 2.13 as shipped by Debian was not built with
--enable-experimental-malloc, so it doesn't use arenas.  This can
substantially decrease RSS usage compared to later versions.  You can
get similar behavior by setting the MALLOC_ARENA_MAX environment
variable to 1 or 2.

Debian 10 also adds a thread cache, which further increases RSS size.
See the manual

  <https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html>

for details how to change thread cache behavior.

Thanks,
Florian