[CentOS] Transparent HugePages question

Wed Aug 24 15:03:02 UTC 2016
Laurentiu Soica <laurentiu at soica.ro>


I have a CentOS 7 installation on baremetal with 2 CPUs, 10 cores each and
HT enabled, 128 GB RAM.

The system has transparent hugetables enabled.

cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never

The system reports anonymous hugepages pages usage and a size of hugepage
of 2048Kb

cat /proc/meminfo |grep -i hugepages|grep AnonHugePages
AnonHugePages:  35491840 kB

cat /proc/meminfo |grep -i hugepages|grep Hugepagesize
Hugepagesize:       2048 kB

Anyway, checking the /proc/<pid>/smaps for each and every process on the
system, the KernelPageSize reports 4K pages only.

for i in `ls /proc/|egrep '[0-9]+'` ; do grep  'KernelPageSize:    '
/proc/$i/smaps; done|grep  '        4 kB'|wc -l
for i in `ls /proc/|egrep '[0-9]+'` ; do grep  'KernelPageSize:    '
/proc/$i/smaps; done|grep  -v '        4 kB'|wc -l

So it turns out that even is I have the THP enabled the pages still have a
size of 4K .

Is there any extra setup in order to get 2MB pages ?

Laurentiu Soica