Hi Wilco,

I had a test application demonstrating the problem.
I include it in attach.
From my particular interest in the tunable this is the difference:

# GLIBC_TUNABLES=glibc.pthread.stack_hugetlb=0 ./tststackalloc 1
Page size: 4 kB, 2 MB huge pages
Will attempt to align allocations to make stacks eligible for huge pages
pid: 3482023 (/proc/3482023/smaps)
stack_size = 2097152, 0x200000
Creating 128 threads...
RSS: 448 pages (1835008 bytes = 1 MB)
Press enter to exit...

# GLIBC_TUNABLES=glibc.pthread.stack_hugetlb=1 ./tststackalloc 1
Page size: 4 kB, 2 MB huge pages
Will attempt to align allocations to make stacks eligible for huge pages
pid: 3482254 (/proc/3482254/smaps)
stack_size = 2097152, 0x200000
Creating 128 threads...
RSS: 65891 pages (269889536 bytes = 257 MB)
Press enter to exit...

Regards,
Cupertino