Arch Linux

MilanKnizek

Member

Registered: 2005-12-13

Posts: 88

[SOLVED] What sets default I/O scheduler for disks?

Hi,

having read the Wiki https://wiki.archlinux.org/index.php/So … _Scheduler , my attention got caught by the current I/O schedulers for my disks:

SSD (two partitiotions: / and /boot, both ext4):

# cat /sys/block/sda/queue/scheduler
noop deadline [cfq]

2 HDDs (part of ZFS mirror pool, partitioned by ZFS itself, mounted automatically on import by ZFS):

# cat /sys/block/sdb/queue/scheduler
[noop] deadline cfq

I am about to create my own udev.rules to set noop and cfq for SSD and HDD, respectively. I just wonder, why all of them are not [cfq], which should be the default?

P.S. I grepped all files in /etc for "noop" and "cfq" to make sure it is not some of my setting forgotten in time. And found nothing.

Last edited by MilanKnizek (2015-04-22 08:32:59)

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Milan Knizek
http://knizek.net

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,597

Website

Re: [SOLVED] What sets default I/O scheduler for disks?

The kernel config does I believe.

% zgrep -i iosched /proc/config.gz
CONFIG_IOSCHED_NOOP=y
CONFIG_IOSCHED_DEADLINE=y
CONFIG_IOSCHED_CFQ=y
CONFIG_CFQ_GROUP_IOSCHED=y
CONFIG_DEFAULT_IOSCHED="cfq"

Perhaps zpools default to noop somehow.

Last edited by graysky (2015-04-22 07:40:35)

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MilanKnizek

Member

Registered: 2005-12-13

Posts: 88

Re: [SOLVED] What sets default I/O scheduler for disks?

Thanks for the quick response and suggestion. Quick googling revealed it is ZFS that sets "noop" scheduler as long as its pools are occupying the whole disk device.

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Milan Knizek
http://knizek.net