Thank you for the update. I am then not sure why it is also "wrong" in
CentOS 7 guest. The inconsistency with other Linux distributions is what
I am concerned about...
# uname -a
Linux centos7-vm2 3.10.0-123.4.2.el7.x86_64 #1 SMP
Mon Jun 30 16:09:14 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
# cat /sys/block/vda/queue/scheduler
noop [deadline] cfq
# ./Linux-check-IO-scheduler-and-discard-support.pl
INFO: File systems and raids
NAME FSTYPE LABEL UUID
MOUNTPOINT
sr0
vda
├─vda1 xfs
a1652174-58b6-4e97-a3ca-4a2160a31100 /boot
└─vda2 LVM2_member
fVCpR3-mtm0-J1KU-XG56-IvOx-9Use-tqS0o2
├─centos_centos7--vm2-swap swap
ad6f9fd9-59a5-49b2-afe9-531a8b74a446 [SWAP]
└─centos_centos7--vm2-root xfs
63a2a109-cb5a-4b75-ac63-b903d81df633 /
INFO: Block devices
NAME ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED
RQ-SIZE RA WSAME
sr0 0 512 0 512 512 1 cfq
128 128 0B
vda 0 512 0 512 512 1
deadline 128 4096 0B
├─vda1 0 512 0 512 512 1
deadline 128 4096 0B
└─vda2 0 512 0 512 512 1
deadline 128 4096 0B
├─centos_centos7--vm2-swap 0 512 0 512 512 1
128 4096 0B
└─centos_centos7--vm2-root 0 512 0 512 512 1
128 4096 0B
INFO: I/O elevator (scheduler) and discard support summary
INFO: Hard Disk vda configured with I/O scheduler "deadline"
All other KVM guests that I run exhibit different reports from Ubuntu
14.01:
OpenSUSE Linux 13.1 (3.11.10-17.x86_64 #1 SMP PREEMPT)
Oracle Linux 6.5 (3.8.13-35.1.2.el6uek.x86_64 #2 SMP)
CentOS Linux 7.0.1406 (3.10.0-123.4.2.el7.x86_64 #1 SMP)
Regards,
Dusan
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You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to util-linux in Ubuntu.
https://bugs.launchpad.net/bugs/1346687
Title:
Ubuntu 14 KVM Guest I/O Elevator Non-configurable
Status in “util-linux” package in Ubuntu:
Invalid
Bug description:
Ubuntu 14.04 guest runs pretty much standard standard configuration:
KVM hypervisor, ACPI and APIC enabled, virtio disk bus, raw storage
format...
While running this project, I am also involved in testing SSD drives
across different Linux distributions and their support for discard
option (TRIM).
To cut the story short, Ubuntu-based KVM guest did not set any
scheduler on the boot disk vda):
# lsblk -io KNAME,TYPE,SCHED,ROTA,DISC-GRAN,DISC-MAX
KNAME TYPE SCHED ROTA DISC-GRAN DISC-MAX
sr0 rom deadline 1 0B 0B
vda disk 1 0B 0B
vda1 part 1 0B 0B
vda2 part 1 0B 0B
vda5 part 1 0B 0B
dm-0 lvm 1 0B 0B
dm-1 lvm 1 0B 0B
That is in stark contrast with other distributions running almost
identical KVM guest configuration (with the exception of the root file
system using BTRFS instead of EXT4 on SUSE).
Oracle Linux 6.5:
# lsblk -io KNAME,TYPE,SCHED,ROTA,DISC-GRAN,DISC-MAX
KNAME TYPE SCHED ROTA DISC-GRAN DISC-MAX
sr0 rom deadline 1 0B 0B
vda disk deadline 1 0B 0B
vda1 part deadline 1 0B 0B
vda2 part deadline 1 0B 0B
dm-0 lvm 1 0B 0B
dm-1 lvm 1 0B 0B
OpenSUSE 13.1:
# lsblk -io KNAME,TYPE,SCHED,ROTA,DISC-GRAN,DISC-MAX
KNAME TYPE SCHED ROTA DISC-GRAN DISC-MAX
sr0 rom cfq 1 0B 0B
vda disk cfq 1 0B 0B
vda1 part cfq 1 0B 0B
vda2 part cfq 1 0B 0B
dm-0 lvm 1 0B 0B
dm-1 lvm 1 0B 0B
Indeed, checking elevator capabilities for boot disk on Ubuntu KVM
guest showed:
# cat /sys/block/vda/queue/scheduler
none
Other Linux distributions show more options:
# cat /sys/block/vda/queue/scheduler
noop deadline [cfq]
As well, attempts to change the elevator on Ubuntu guest fail. For
example:
# echo noop > /sys/block/vda/queue/scheduler
# echo $?
0
# cat /sys/block/vda/queue/scheduler
none
Setting it globally in /etc/default/grub and updating it via update-
grub2 fails too.
In the meantime, to automate check of elevators (schedulers) and
discard support for SSD drives and thin-provisioned volumes on Linux,
I wrote simple Perl script:
http://www.circlingcycle.com.au/Unix-sources/Linux-check-IO-scheduler-
and-discard-support.pl.txt
Part of the results on RHEL 6.5 server would look like:
INFO: I/O elevator (scheduler) and discard support summary
INFO: Hard Disk sdb configured with I/O scheduler "cfq"
INFO: SSD sda configured with I/O scheduler "deadline" supports discard
operation
INFO: Hard Disk sdc configured with I/O scheduler "cfq"
INFO: Hard Disk sdi configured with I/O scheduler "cfq"
INFO: Hard Disk sdh configured with I/O scheduler "cfq"
The Ubuntu KVM guest runs latest paches:
Linux ubuntu14-vm2.circlingcycle.com.au 3.13.0-24-generic
#47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
Regards,
Dusan Baljevic VK2COT
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