Bug#593720: Fwd: Deadline as default scheduler?
Package: linux-2.6
Version: 2.6.35-1~experimental.2
Severity: normal
This bug report is just a reminder that comes from a message i sent on
d-k mailing list: appended inline my initial message and the reply from
Ben Hutchings.
The original message was about 2.6.35-1~experimental.1, but in
experimental.2 the CFQ scheduler is yet configured as module and
deadline is the default scheduler (with evident negative impact on
responsiveness, at least on my not so young Pentium M 1,6 GHz).
Cesare.
-------- Original Message --------
Subject: Deadline as default scheduler?
Date: Tue, 10 Aug 2010 00:04:44 +0200
From: Cesare Leonardi <celeonar@gmail.com>
To: debian-kernel@lists.debian.org
Hi all.
I've noted some changes in the scheduler configuration of
2.6.35-trunk-686 and i wonder if they are erroneous or not, since their
effect are rather evident and i've seen no discussion on d-k.
I was filing a bug but i preferred to ask on the mailing list first.
--- /boot/config-2.6.35-rc6-686 2010-07-26 13:09:56.000000000 +0200
+++ /boot/config-2.6.35-trunk-686 2010-08-06 18:13:52.000000000 +0200
@@ -221,11 +222,12 @@
#
CONFIG_IOSCHED_NOOP=y
CONFIG_IOSCHED_DEADLINE=y
-CONFIG_IOSCHED_CFQ=y
-# CONFIG_DEFAULT_DEADLINE is not set
-CONFIG_DEFAULT_CFQ=y
+CONFIG_IOSCHED_CFQ=m
+CONFIG_CFQ_GROUP_IOSCHED=y
+CONFIG_DEFAULT_DEADLINE=y
+# CONFIG_DEFAULT_CFQ is not set
# CONFIG_DEFAULT_NOOP is not set
-CONFIG_DEFAULT_IOSCHED="cfq"
+CONFIG_DEFAULT_IOSCHED="deadline"
Why setting deadline as default scheduler? And why configuring cfq as
module?
In a desktop usage, with a pentium M 1,6 GHz and 1 GB ram, the system is
clearly worse in responsiveness, a bit jerky in particular when i type
on the keyboard: occasionaly i can see the effect of what i type with a
delay of some tenth of second.
Are there other distros not using cfq as default scheduler?
Ciao.
Cesare.
-------- Reply from Ben --------
Subject: Re: Deadline as default scheduler?
Date: Tue, 10 Aug 2010 01:58:14 +0100
From: Ben Hutchings <ben@decadent.org.uk>
To: Cesare Leonardi <celeonar@gmail.com>, Maximilian Attems
<mattems@hep.itp.tuwien.ac.at>
CC: debian-kernel@lists.debian.org
[...]
> Why setting deadline as default scheduler? And why configuring cfq as
> module?
This is due to enabling BLK_CGROUP:
config IOSCHED_CFQ
tristate "CFQ I/O scheduler"
# If BLK_CGROUP is a module, CFQ has to be built as module.
depends on (BLK_CGROUP=m && m) || !BLK_CGROUP || BLK_CGROUP=y
Max, we have to make BLK_CGROUP=y or disable it completely.
Ben.
--
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.
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