tuned-adm fails to set kernel scheduler for block devices

This document (7024212) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server for SAP Applications 12 SP 4

Situation

In /var/log/tuned/tuned.log the following error is observed

2019-10-04 17:33:53,280 ERROR tuned.utils.commands: Writing to file /sys/block/vda/queue/scheduler error: [Errno 22] Invalid argument

2019-10-04 17:33:53,281 ERROR tuned.utils.commands: Writing to file /sys/block/vdb/queue/scheduler error: [Errno 22] Invalid argument

Checking the scheduler settings for the block devices show they are different from the settings in the selected tuned profile:

testvm:~ # lsblk -o 'NAME,KNAME,MAJ:MIN,FSTYPE,LABEL,RO,RM,MODEL,SIZE,OWNER,GROUP,MODE,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-SEC,ROTA,SCHED,MOUNTPOINT'

NAME KNAME MAJ:MIN FSTYPE LABEL RO RM MODEL SIZE OWNER GROUP MODE ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED MOUNTPOINT

vda vda 254:0 0 0 36G root disk brw-rw---- 0 512 0 512 512 1 mq-deadline

├─vda1 vda1 254:1 ext3 logs 0 0 2G root disk brw-rw---- 0 512 0 512 512 1 mq-deadline /var/log/local

└─vda2 vda2 254:2 swap 0 0 33G root disk brw-rw---- 0 512 0 512 512 1 mq-deadline [SWAP]

vdb vdb 254:16 1 0 256K root disk brw-rw---- 0 512 0 512 512 1 mq-deadline

Checking the available scheduler settings show different options than the well known ones (deadline, noop, cfq):

testvm:~ # cat /sys/block/vd*/queue/scheduler

[mq-deadline] kyber bfq none

Resolution

An override profile may be created as /etc/tuned/<profile-name>/profile.conf:

During the next steps the <profile-name> "sap-hana" will be used.

mkdir /etc/tuned/sap-hana/
cp /usr/lib/tuned/sap-hana/tuned.conf /etc/tuned/sap-hana/tuned.conf
Change the line "elevator = " to the preferred scheduler
Change the line "script = script.sh" to "script = /usr/lib/tuned/<profile-name>/script.sh"
Activate the new settings using tuned-adm profile <profile-name>:

tuned-adm profile sap-hana

Cause

The situation described above was seen when a KVM VM using tuned was configured using the noop scheduler but when checking showed mq-deadline despite correct

setting in the respective tuned.conf file. Due to changes in the kernel new multiqueue I/O schedulers were introduced and the naming changed, this

is why "invalid argument" is reported in tuned.log as an

echo noop > /sys/block/vda/queue/scheduler

is no longer accepted as valid option.

Additional Information

This example demonstrates the change of the kernel scheduler currently using the cfq scheduler. The correct scheduler in this VM scenario would be noop:

sles4sap12sp4:~ # lsblk -o 'NAME,KNAME,MAJ:MIN,FSTYPE,LABEL,RO,RM,MODEL,SIZE,OWNER,GROUP,MODE,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-SEC,ROTA,SCHED,MOUNTPOINT'

NAME KNAME MAJ:MIN FSTYPE LABEL RO RM MODEL SIZE OWNER GROUP MODE ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED MOUNTPOINT

sda sda 8:0 0 0 Virtual disk 50G root disk brw-rw---- 0 512 0 512 512 1 cfq

├─sda1 sda1 8:1 swap 0 0 2G root disk brw-rw---- 0 512 0 512 512 1 cfq [SWAP]

└─sda2 sda2 8:2 btrfs 0 0 48G root disk brw-rw---- 0 512 0 512 512 1 cfq /

sles4sap12sp4:~ # mkdir /etc/tuned/sap-hana/

sles4sap12sp4:~ # cp /usr/lib/tuned/sap-hana/tuned.conf /etc/tuned/sap-hana/tuned.conf

sles4sap12sp4:~ # vi /etc/tuned/sap-hana/tuned.conf

sles4sap12sp4:~ # cat /etc/tuned/sap-hana/tuned.conf

# basic tuned configuration for SAP NetWeaver, SAP HANA and HANA based products.

# Additional parameters are tuned by script.sh

# For a brief explanation of the parameters, please have a look at the end of

# the central sapconf configuration file /etc/sysconfig/sapconf

[main]

summary=Optimize for SAP NetWeaver, SAP HANA and HANA based products

[cpu]

#governor = performance

#energy_perf_bias = performance

#min_perf_pct = 100

force_latency = 70

[disk]

elevator = noop

[script]

script = /usr/lib/tuned/sap-hana/script.sh

sles4sap12sp4:~ # tuned-adm profile sap-hana

sles4sap12sp4:~ # lsblk -o 'NAME,KNAME,MAJ:MIN,FSTYPE,LABEL,RO,RM,MODEL,SIZE,OWNER,GROUP,MODE,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-SEC,ROTA,SCHED,MOUNTPOINT'

NAME KNAME MAJ:MIN FSTYPE LABEL RO RM MODEL SIZE OWNER GROUP MODE ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED MOUNTPOINT

sda sda 8:0 0 0 Virtual disk 50G root disk brw-rw---- 0 512 0 512 512 1 noop

├─sda1 sda1 8:1 swap 0 0 2G root disk brw-rw---- 0 512 0 512 512 1 noop [SWAP]

└─sda2 sda2 8:2 btrfs 0 0 48G root disk brw-rw---- 0 512 0 512 512 1 noop /

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