Huge pages are stolen by another process

tikit · 06-07-2013, 05:48 AM

Hello all,

We would like to configure Oracle to use hugepages. Our /etc/sysctl.conf looks as follows

Code:

vm.nr_hugepages = 2563
vm.hugetlb_shm_group = 111

The problem is that even though Oracle is not running there are already some hugepages allocated.

Code:

cat /proc/meminfo | egrep -i huge
HugePages_Total:    2563
HugePages_Free:     1752
HugePages_Rsvd:     1752
HugePages_Surp:      467
Hugepagesize:       2048 kB

I found out that it is a tomcat process but the tomcat user is not in the group configured by the vm.hugetlb_shm_group parameter. So how is it possible that the process gets the hugepages?

We use Suse linux enterprise server 11 SP1 kernel 2.6.32.12-0.7

Sigg3.net · 06-09-2013, 08:14 AM

I am NOT an expert, but in terms of operating systems free ram is _useless_, so modern operating systems will fill memory when available in order to perform better. Am I off the field? Not sure. Just a thought

tikit · 06-11-2013, 01:31 AM

I think this is not the case when a free RAM can be allocated by another process. Otherwise I don't know what the parameter vm.hugetlb_shm_group is suppossed to be used for. The problem is that when the tomcat process is started before the Oracle, there is not enough free hugepages for Oracle.