Configuring Huge Pages In Red Hat Enterprise Linux 3 - Red Hat ENTERPRISE LINUX 5.1 - LINUX ORACLE Tuning Manual

Oracle 9i and 10g tuning guide

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Thus, Big Pages cannot be larger than Highmem. The total amount of memory in the high region can

be obtained by reading the memory statistic HighTotal from the /proc/meminfo file:

$ grep "HighTotal" /proc/meminfo

HighTotal:

9043840 kB

The Big Pages feature can be enabled with the following command:

# echo "1" > /proc/sys/kernel/shm-use-bigpages

Alternatively, you can use sysctl(8) to change it:

# sysctl -w kernel.shm-use-bigpages=1

To make the change permanent, add the following line to the file /etc/sysctl.conf. This file is

used during the boot process.

echo "kernel.shm-use-bigpages=1" >> /etc/sysctl.conf

Setting kernel.shm-use-bigpages to 2 enables the Big Pages feature for the shared memory file

system (shmfs). Setting kernel.shm-use-bigpages to 0 disables the Big Pages feature. In Red

Hat Enterprise Linux 2.1 the size of the Big Pages pool is configured by adding a parameter to the

kernel boot command. For example, if you use GRUB and you want to set the Big Pages pool to 1000

MB, edit the /etc/grub.conf file and add the "bigpages" parameter as follows:

default=0

timeout=10

title Red Hat Linux Advanced Server (2.4.9-e.40enterprise)

root (hd0,0)

kernel /vmlinuz-2.4.9-e.40enterprise ro root=/dev/sda2 bigpages=1000MB

initrd /initrd-2.4.9-e.40enterprise.img

title Red Hat Linux Advanced Server (2.4.9-e.40smp)

root (hd0,0)

kernel /vmlinuz-2.4.9-e.40smp ro root=/dev/sda2

initrd /initrd-2.4.9-e.40smp.img

After this change the system must be rebooted:

# shutdown -r now

After a system reboot the 1000 MB Big Pages pool should show up under BigPagesFree in /proc/

meminfo.

grep BigPagesFree /proc/meminfo

Note that if HighTotal in /proc/meminfo is 0 KB, then BigPagesFree will always be 0 KB as well

since Big Pages can only be allocated and pinned above approximately 860MB of physical RAM.

14.6. Configuring Huge Pages in Red Hat Enterprise Linux

Before configuring Big Pages, ensure to have read