What is hugepages
HugePages is a feature integrated into the Linux kernel with release 2.6. This feature basically provides the alternative to the 4K page size (16K for IA64) providing bigger pages. HugePages is a method to have larger pages where it is useful for working with very large memory.
Configure hugepages by using the kernel tunable vm.nr_hugepages
1. Edit /etc/sysctl.conf file and specify the number of hugepages in the nr_hugepages parameter. The entry makes the parameter persist across reboots but does not come into effect until you run the ‘sysctl -p’ command described in the next step.
# vi /etc/sysctl.conf vm.nr_hugepages = 10
2. Execute ‘sysctl -p’ command to enable the hugepages parameter.
# sysctl -p ... vm.nr_hugepages = 10
Verify
To verify the hugepages parameter setting, use either for the 2 methods given below:
1. check for the file /proc/meminfo :
# cat /proc/meminfo | grep Huge HugePages_Total: 10 HugePages_Free: 10 HugePages_Rsvd: 0 Hugepagesize: 2048 kB
where:
HugePages_Total – the size of the pool of huge pages.
HugePages_Free – the number of huge pages in the pool that are not yet used.
HugePages_Rsvd – the number of huge pages committed to be allocated from the pool but no allocation has yet been made.
HugePages_Surp – is short for “surplus,” and is the number of huge pages in the pool above the value in /proc/sys/vm/nr_hugepages. The maximum number of surplus huge pages is controlled by /proc/sys/vm/nr_overcommit_hugepages.
2. Use the sysctl command :
# sysctl a | grep nr_hugepages vm.nr_hugepages = 10
How to calculate hugepages
Used hugepages can be calculated by below method. Use the values from the outpur of ‘cat /proc/meminfo’ in the formula below.
HugePages_Total - HugePages_Free = HugePages_Used