Linux Kernel Tuning for Oracle 10G
==========================
Note:
Physical memory is 256GB
SHMALL is 240GB in sysctl.conf
SHMMAX is 210GB in sysctl.conf
sga_max_size is 200GB in init.ora
processes is 5000 in init.ora
- Make sure i/o scheduler to deadline (/etc/grub.conf)
# cat /sys/block/sd?/queue/scheduler
noop [deadline] cfq
title Oracle Linux Server (2.6.32-300.25.1.el6uek.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-300.25.1.el6uek.x86_64 ro root=LABEL=/ elevator=deadline
initrd /initramfs-2.6.32-300.25.1.el6uek.x86_64.img
Note. deadline scheduler is default in OL5 UEK2Q5.
- Make sure transparent_hugepage is disabled (/etc/grub.conf)
title Oracle Linux Server (2.6.32-300.25.1.el6uek.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-300.25.1.el6uek.x86_64 ro root=LABEL=/ transparent_hugepage=never
initrd /initramfs-2.6.32-300.25.1.el6uek.x86_64.img
Note: there is no /sys/kernel/mm/transparent_hugepage in OL5 UEK2Q5
https://oss.oracle.com/el5/docs/RELEASE-NOTES-UEK2-QU5-en.html
- Kernel shared memory
kernel.shmall = 240*1024*1024*1024/4096
kernel.shmmax = 210*1024*1024*1024
- Kernel semaphores
check processes parameter in init.ora
SEMMSL = processes + 10
SEMMNS = processes * 128
SEMOPM = processes + 10
SEMMNI = 128
kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI
- Enable manual HugePages
check sga_max_size parameter in init.ora
X = Hugepagesize (# grep Hugepage /proc/meminfo)
Y = sga_max_size (in KB)
Z = Y / X
vm.nr_hugepages = Z + 10
- Put this settings into /etc/sysctl.conf
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 262144
net.core.wmem_default = 262144
net.core.rmem_max = 262144
net.core.wmem_max = 262144
net.ipv4.tcp_rmem = 4096 262144 4194304
net.ipv4.tcp_wmem = 4096 262144 262144
kernel.shmall = 62914560
kernel.shmmax = 225485783040
kernel.shmmni = 4096
kernel.sem = 5010 641280 5010 128
vm.nr_hugepages = 102410
vm.swappiness = 0
vm.dirty_background_ratio = 3
vm.dirty_ratio = 15
vm.dirty_expire_centisecs = 500
vm.dirty_writeback_centisecs = 100
vm.min_free_kbytes = 1024
- Set ulimit parameter for oracle (/etc/security/limits.conf)
Note. memlock is sga_max_size in KB.
oracle soft memlock 209715200
oracle hard memlock 209715200
oracle soft nofile 63536
oracle hard nofile 63536
oracle soft nproc 16384
oracle hard nproc 16384
- Reboot your server and start your database
- Make sure oracle use hugepages
# grep Huge /proc/meminfo
HugePages_Total: 102410
HugePages_Free: 56268
HugePages_Rsvd: 55235
HugePages_Surp: 0
Hugepagesize: 2048 kB
- Check the HugePages_Rsvd, if it is still 0, try to reduce your sga_max_size parameter in pfile/spfile without change sysctl.conf and limits.conf anymore.
For example, try sga_max_size is 198GB.
Shutdown and start the database, and make sure HugePages_Rsvd is not empty.
