linux 关闭透明大页

oracle 建议关闭透明大页

Because Transparent HugePages are known to cause unexpected node reboots and performance problems with RAC,

Oracle strongly advises to disable the use of Transparent HugePages.

In addition, Transparent Hugepages may cause problems even in a single-instance database environment with unexpected performance problems or delays.

As such, Oracle recommends disabling Transparent HugePages on all Database servers running Oracle

参考mos 

ALERT: Disable Transparent HugePages on SLES11, RHEL6, RHEL7, OL6, OL7, and UEK2 and above (Doc ID 1557478.1)

Oracle Linux 7 - How to disable Transparent HugePages for RHCK kernel? (Doc ID 2066217.1)

[root@ht01 ~]# cat /etc/grub.conf 
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/mapper/vg_redis01-lv_root
#          initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Oracle Linux Server Unbreakable Enterprise Kernel (4.1.12-61.1.28.el6uek.x86_64)
	root (hd0,0)
	kernel /vmlinuz-4.1.12-61.1.28.el6uek.x86_64 ro root=/dev/mapper/vg_redis01-lv_root rd_NO_LUKS rd_LVM_LV=vg_redis01/lv_swap LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 rd_LVM_LV=vg_redis01/lv_root  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet transparent_hugepage=never
	initrd /initramfs-4.1.12-61.1.28.el6uek.x86_64.img
title Oracle Linux Server Red Hat Compatible Kernel (2.6.32-696.el6.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=/dev/mapper/vg_redis01-lv_root rd_NO_LUKS rd_LVM_LV=vg_redis01/lv_swap LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_redis01/lv_root  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet  
	initrd /initramfs-2.6.32-696.el6.x86_64.img

[root@ht01 ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
[root@ht01 ~]# grep Huge /proc/meminfo
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB

　　如果linux 没有关闭透明大页，rac 节点重启  需检查ocssd.log /ocssd.trc

2013-05-01 14:30:45.255: [    CSSD][224204544]clssscMonitorThreads clssnmvKillBlockThread not scheduled for 7500 msecs
2013-05-01 14:30:46.945: [    CSSD][224204544]clssscMonitorThreads clssnmvWorkerThread not scheduled for 8030 msecs