Noop Scheduler, for those of you who don’t know, is the simplest I/O scheduler for Linux. NOOP scheduler inserts all incoming I/O requests into a simple FIFO queue and implements request merging. In other words, the scheduler assumes that the host is unaware of how to productively re-order requests. There for, noop handles all IO scheduling.
Lets enable enable noop.
First, well need to see if noop is currently being used. Well redirect it to a file and then cat it.
$ echo 'noop' > sys/block/sda/queue/scheduler
$ cat /sys/block/sda/queue/scheduler
You should get something like this:
[root@node1~]# cat /sys/block/sda/queue/scheduler [noop] deadline cfq
As you can see my server is already configured to use noop.
You can setup noop by editing the following /etc/default/grub.
[root@node1 ~]# cat /etc/default/grub GRUB_TIMEOUT=5 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=cl_node1/root rd.lvm.lv=cl_node1/swap elevator=noop" GRUB_DISABLE_RECOVERY="true" [root@node1 ~]#
Next you will need to rebuild the grub2 config file. (boot.grub2/grub.cfg)
enter the following
[root@node1 ~]# grub2-mkconfig -o /boot/grub2/grub.cfg Generating grub configuration file ... Found linux image: /boot/vmlinuz-3.10.0-693.5.2.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-693.5.2.el7.x86_64.img Found linux image: /boot/vmlinuz-3.10.0-693.2.2.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-693.2.2.el7.x86_64.img Found linux image: /boot/vmlinuz-3.10.0-514.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-514.el7.x86_64.img Found linux image: /boot/vmlinuz-0-rescue-edf3cb748ba24f44b2453ec41af756ef Found initrd image: /boot/initramfs-0-rescue-edf3cb748ba24f44b2453ec41af756ef.img done [root@node1 ~]#
Reboot the system to verify that it works. There should be nothing in the directory since noop doesn’t use tunables.
[root@node1 ~]# ls /sys/block/sda/queue/iosched/
