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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.
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: tuned
Version: 7.2
Hardware: Unspecified
OS: Linux
Target Milestone: rc
: ---
Assignee: Jaroslav Škarvada
QA Contact: qe-baseos-daemons
Depends On:
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:
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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 <>.)  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):


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?

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