IO Scheduler: Difference between revisions
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= Introduction | == Introduction == | ||
The Linux kernel, the core of the operating system, is responsible for controlling disk access by using kernel IO scheduling. | The Linux kernel, the core of the operating system, is responsible for controlling disk access by using kernel IO scheduling. | ||
| Line 5: | Line 5: | ||
This article explains how-to change the IO scheduler without recompiling the kernel and without restart. | This article explains how-to change the IO scheduler without recompiling the kernel and without restart. | ||
= Check the currently used IO scheduler | == Check the currently used IO scheduler == | ||
cat /sys/block/sda/queue/scheduler | cat /sys/block/sda/queue/scheduler | ||
| Line 11: | Line 11: | ||
noop anticipatory [deadline] cfq | noop anticipatory [deadline] cfq | ||
For example the scheduler '''deadline''' delivers best performance on hardware raid and SAN environments. While '''noop''' delivers better performance for SSDs. | |||
= Switching IO Schedulers on runtime | == Switching IO Schedulers on runtime == | ||
Set the scheduler for /dev/sda to Deadline: | Set the scheduler for /dev/sda to Deadline: | ||
| Line 23: | Line 23: | ||
echo cfq > /sys/block/sda/queue/scheduler | echo cfq > /sys/block/sda/queue/scheduler | ||
= Set IO Schedulers permanently | == Set IO Schedulers permanently == | ||
In order to choose a new default scheduler you need to add the following into your /etc/default/grub: | In order to choose a new default scheduler you need to add the following into your /etc/default/grub: | ||
| Line 29: | Line 29: | ||
nano /etc/default/grub | nano /etc/default/grub | ||
GRUB_CMDLINE_LINUX_DEFAULT="... elevator=deadline" | |||
or: | or: | ||
GRUB_CMDLINE_LINUX_DEFAULT="... elevator=cfq" | |||
After you change /etc/default/grub you need to run update-grub to apply changes: | After you change /etc/default/grub you need to run update-grub to apply changes: | ||
| Line 39: | Line 39: | ||
update-grub | update-grub | ||
= Links = | == Links == | ||
*http://en.wikipedia.org/wiki/Deadline_scheduler | *http://en.wikipedia.org/wiki/Deadline_scheduler | ||
*http://en.wikipedia.org/wiki/CFQ | *http://en.wikipedia.org/wiki/CFQ | ||
*https://cromwell-intl.com/open-source/performance-tuning/disks.html | |||
[[Category: HOWTO]][[Category: | [[Category: HOWTO]] [[Category:System Administration]] | ||
Latest revision as of 07:38, 11 January 2019
Introduction
The Linux kernel, the core of the operating system, is responsible for controlling disk access by using kernel IO scheduling.
This article explains how-to change the IO scheduler without recompiling the kernel and without restart.
Check the currently used IO scheduler
cat /sys/block/sda/queue/scheduler
noop anticipatory [deadline] cfq
For example the scheduler deadline delivers best performance on hardware raid and SAN environments. While noop delivers better performance for SSDs.
Switching IO Schedulers on runtime
Set the scheduler for /dev/sda to Deadline:
echo deadline > /sys/block/sda/queue/scheduler
Set the scheduler for /dev/sda to CFQ:
echo cfq > /sys/block/sda/queue/scheduler
Set IO Schedulers permanently
In order to choose a new default scheduler you need to add the following into your /etc/default/grub:
nano /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="... elevator=deadline"
or:
GRUB_CMDLINE_LINUX_DEFAULT="... elevator=cfq"
After you change /etc/default/grub you need to run update-grub to apply changes:
update-grub