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Bug #25819

autotune is evil

Added by Rob VanHooren about 3 years ago. Updated about 3 years ago.

Status:
Closed: Behaves correctly
Priority:
No priority
Assignee:
Release Council
Category:
OS
Target version:
Seen in:
Severity:
New
Reason for Closing:
Reason for Blocked:
Needs QA:
Yes
Needs Doc:
Yes
Needs Merging:
Yes
Needs Automation:
No
Support Suite Ticket:
n/a
Hardware Configuration:
ChangeLog Required:
No

Description

goal: fine-tune available RAM, reducing arc_max to 20GB

observed behaviour: edits to revise autotuned vfs.zfs.arc_max are ignored.

expected behaviour: edits to vfs.zfs.arc_max values are accepted.

reproduce:
(system->advanced->autotune->enable)
(reboot)
(system->tunables->edit->vfs.zfs.arc_max->21474836480->save)

History

#1 Updated by Rob VanHooren about 3 years ago

  • File debug-tape-20170908175843.txz added

#2 Updated by Rob VanHooren about 3 years ago

  • Subject changed from arc_max edits ignored to arc_max value edits ignored

update: of interest, edits to the tuneable's comment text are saveable, whereafter attempted edits to the tuneable's value revert comment text to default ("Generated by autotune")

#3 Updated by Rob VanHooren about 3 years ago

  • Seen in changed from Unspecified to 11.0-U3

#4 Updated by Rob VanHooren about 3 years ago

  • Subject changed from arc_max value edits ignored to autotune is evil

hmmm.

it seems autotune is evil, and overrides/re-writes any edits made to any of the tuneables it owns.
(i.e., edits made do not persist)

... if true, why are they editable at_all ?

suggest: param edits are respected or autotune-owned params are masked as read-only.

#5 Updated by Dru Lavigne about 3 years ago

  • Status changed from Unscreened to Closed: Behaves correctly
  • Target version set to N/A
  • Private changed from Yes to No

This is considered to be a "feature", see http://doc.freenas.org/11/system.html#autotune. In other words, either let autotune attempt to autotune the system for you, or don't use autotune and put in your Tunables manually.

#6 Updated by Dru Lavigne about 3 years ago

  • File deleted (debug-tape-20170908175843.txz)

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