Bug #54

metaslab_min_alloc_size may be too big

Added by Garrett D'Amore over 3 years ago. Updated over 2 years ago.

Status:Closed Start date:2010-08-18
Priority:Normal Due date:
Assignee:- % Done:

0%

Category:- Spent time: -
Target version:-
Difficulty:Medium Tags:needs-triage

Description

See bugs.opensolaris.org: CR 6962304. It seems like we could adjust this tunable to be a bit more sane.

The current default value of metaslab_min_alloc_size is 10M

Several systems which have pools that are in the neighborhood of 70% or so full
were observed spending a lot of time in metaslab-related code and were generally seen as slow.

Someone suggested patching metaslab_min_alloc_size to 4K, and this has significantly reduced the amount of cpu used by zfs and made the systems significantly more responsive.

Looks like the default value is wrong.

Workaround:

Add the following to /etc/system and reboot:

  • Work around 6962304
    set zfs:metaslab_min_alloc_size=0x1000

History

Updated by Garrett D'Amore over 2 years ago

  • Status changed from New to Closed
  • Difficulty set to Medium
  • Tags set to needs-triage

Turns out this tunable is made irrelevant as a result of a change to use the metaslab_df_ops allocator. We don't need to change it. I'm closing this bug.

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