How to
Environment
- Red Hat Enterprise Linux (RHEL) 6
- transparent hugepages (THP)
- tuned
- ktune
Change the kernel setting on /boot/grub/grub.conf
$ sed -i 's/quiet/quiet transparent_hugepage=never/' /boot/grub/grub.conf
reboot your system
$ reboot
check after reboot
$ grep -i never /boot/grub/grub.conf
kernel /boot/vmlinuz-2.6.32-358.el6.x86_64 ro root=UUID=a216d1e5-884f-4e5c-859a-6e2e2530d486 rhgb quiet transparent_hugepage=never
$ cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
always [never]
when it is not taking effect
Issue
- Unable to disable transparent hugepages (THP) even after appending “transparent_hugepage=never” to kernel command line in /boot/grub/grub.conf file.
$ grep -i never /boot/grub/grub.conf
kernel /boot/vmlinuz-2.6.32-358.el6.x86_64 ro root=UUID=a216d1e5-884f-4e5c-859a-6e2e2530d486 rhgb quiet transparent_hugepage=never
$ cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
[always] never
$ grep -i AnonHugePages /proc/meminfo
AnonHugePages: 206848 kB
Resolution
Create a customized tuned profile with disabled THP
$ tuned-adm active
Current active profile: throughput-performance
Service tuned: enabled, running
Service ktune: enabled, running
$ cd /etc/tune-profiles/
$ cp -r throughput-performance throughput-performance-no-thp
$ sed -ie 's,set_transparent_hugepages always,set_transparent_hugepages never,' \
/etc/tune-profiles/throughput-performance-no-thp/ktune.sh
$ grep set_transparent_hugepages /etc/tune-profiles/throughput-performance-no-thp/ktune.sh
set_transparent_hugepages never
$ tuned-adm profile throughput-performance-no-thp
$ cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
always [never]
Alternative: Disable tuned and ktune services.
$ service tuned stop
$ chkconfig tuned off
$ service ktune stop
$ chkconfig ktune of
or
$ tuned-adm off
Root Cause
- The
ktuneservice enablestransparent hugepages(THP) by default for all profiles.
# cat /etc/tune-profiles/enterprise-storage/ktune.sh
#!/bin/sh
. /etc/tune-profiles/functions
start() {
set_cpu_governor performance
set_transparent_hugepages always <<<----
disable_disk_barriers
multiply_disk_readahead 4
return 0
}
stop() {
restore_cpu_governor
restore_transparent_hugepages
enable_disk_barriers
restore_disk_readahead
return 0
}
process $@
Diagnostic
- Verify ktune and tuned services;
$ chkconfig --list |egrep -i "ktune|tuned"
ktune 0:off 1:off 2:off 3:on 4:on 5:on 6:off
tuned 0:off 1:off 2:on 3:on 4:on 5:on 6:off