Note: This is a beta release of Red Hat Bugzilla 5.0. The data contained within is a snapshot of the live data so any changes you make will not be reflected in the production Bugzilla. Also email is disabled so feel free to test any aspect of the site that you want. File any problems you find or give feedback here.
Bug 1361751 - The tuned-adm Command Does Not Change the I/O Scheduler.
Summary: The tuned-adm Command Does Not Change the I/O Scheduler.
Keywords:
Status: ASSIGNED
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: tuned
Version: 7.2
Hardware: Unspecified
OS: Linux
unspecified
low
Target Milestone: rc
: ---
Assignee: Jaroslav Škarvada
QA Contact: qe-baseos-daemons
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-07-30 03:38 UTC by Bernie Hoefer
Modified: 2018-10-26 21:52 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed:


Attachments (Terms of Use)

Description Bernie Hoefer 2016-07-30 03:38:35 UTC
Description of problem:

I'm not sure if this is a bug with RHEL7's tuned-adm command, a feature that just hasn't been completed or a lack of explicitness in the documentation.

In RHEL6, using tuned-adm to change from one profile to another can affect the I/O scheduler that is set.  This is done through tuned's sister service, ktune.

In RHEL7, the functionality of ktune was supposedly built into tuned version 2.  (See <https://access.redhat.com/solutions/2062263>.)  Yet, using the tuned-adm command to activate a profile whose I/O scheduler should be different than the currently set I/O scheduler results in no change.

Reading through the _RHEL7 Performance Tuning Guide_, I don't see references to the I/O scheduler in the tuned profiles' descriptions like I see in the RHEL6 guide.  Likewise, the tuned-profiles man pages are similarly different across both RHEL versions.  Thus, I get the impression that the RHEL7 tuned is not suppose to change the I/O scheduler like the RHEL6 one did.  But nowhere is it explicitly stated.

This is confusing to users who are use to the RHEL6 functionality.


Version-Release number of selected component (if applicable):

tuned-2.5.1-4.el7_2.3.noarch


How reproducible:

On RHEL6, execute these commands to see how tuned-adm changes the I/O scheduler from cfq to deadline by applying the virtual-guest profile:
  echo cfq > /sys/block/sda/queue/scheduler 
  cat /sys/block/sda/queue/scheduler 
  tuned-adm profile virtual-guest
  cat /sys/block/sda/queue/scheduler 
One RHEL7, execute those exact same commands and note that the I/O scheduler does not change.  This is the case for *any* profile chosen, not just the virtual-guest one.  (Even the enterprise-storage profile from the tuned-profiles-compat RPM, which should have the deadline scheduler for compatibility reasons since that is how it was in RHEL6.)


Additional info:

My gut feeling is that this functionality was purposely left out of RHEL7's tuned.  Once that is confirmed -- with hopefully an explanation of why -- I'll change this ticket to request it be documented RHEL7 guides.  Thank you.

Comment 3 Jaroslav Škarvada 2017-01-24 16:56:18 UTC
Thanks for the report. The functionality is still there, and it can be used in custom Tuned profiles, but IIRC we no longer change I/O scheduler in our profiles. IIRC the change was introduced per resolution of bug 922068 (which unfortunately isn't public). Jeremy could you provide more information?


Note You need to log in before you can comment on or make changes to this bug.