[Bug 1850754] Re: ceph-volume lvm list is O(n^2)

Timo Aaltonen tjaalton at ubuntu.com
Fri Dec 13 10:11:50 UTC 2019


Hello Dariusz, or anyone else affected,

Accepted ceph into disco-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/ceph/13.2.7-0ubuntu0.19.04.1 in a
few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-disco to verification-done-disco. If it does not fix
the bug for you, please add a comment stating that, and change the tag
to verification-failed-disco. In either case, without details of your
testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: ceph (Ubuntu Disco)
       Status: New => Fix Committed

** Tags added: verification-needed-disco

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https://bugs.launchpad.net/bugs/1850754

Title:
  ceph-volume lvm list is O(n^2)

Status in Ceph:
  Unknown
Status in Ubuntu Cloud Archive:
  Fix Committed
Status in Ubuntu Cloud Archive queens series:
  Fix Committed
Status in Ubuntu Cloud Archive rocky series:
  New
Status in Ubuntu Cloud Archive stein series:
  New
Status in Ubuntu Cloud Archive train series:
  Fix Committed
Status in ceph package in Ubuntu:
  Fix Released
Status in ceph source package in Bionic:
  Fix Committed
Status in ceph source package in Disco:
  Fix Committed
Status in ceph source package in Eoan:
  Fix Committed

Bug description:
  [Impact]
  ceph-volume lvm calls take too much time and the time grows exponentially.
  A simple call may take several minutes depending on the LV configuration.

  [Test Case]
  1. Create a setup with a large number of disks and logical volumes (e.g. 24)
  2. Call ceph-volume lvm list for one of the disks.
  3. Wait for the call to finish.

  [Regression Potential]
  Patch introduces LV caching, so changing LVs while ceph-volume is running may lead to race conditions.

  [Other Info]
  Original bug description:
   
   * Anything else you think is useful to include
   * Anticipate questions from users, SRU, +1 maintenance, security teams and the Technical Board
   * and address these questions in advance

  ceph-volume lvm list calls take very long time due to the fact it has
  been implemented with O(n^2). This leads to unproportionally long
  execution time taking under consideration the fact that no complex
  computation is needed.

  Steps to reproduce:
  1. Create a setup with a large number of disks and logical volumes (e.g. 24)
  2. Call ceph-volume lvm list for one of the disks.
  3. Wait for the call to finish.

  Expected result:
  Call is executed within seconds at most.

  Actual result:
  Call may take even minutes in some circumstances (large number of disks, some OSDs stopped).

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