[Bug 1906496] Re: mgr can be very slow in a large ceph cluster

[Ponnuvel Palaniyappan]

Patch file for 13.2.9

** Attachment added: "bug1906496.patch-13.2.9"
   https://bugs.launchpad.net/ubuntu/+source/ceph/+bug/1906496/+attachment/5442309/+files/bug1906496.patch-13.2.9

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Title:
  mgr can be very slow in a large ceph cluster

Status in ceph package in Ubuntu:
  In Progress

Bug description:
  upstream implemented a new feature [1] that will check/report those
  long network ping times between osds, but it introduced an issue that
  ceph-mgr might be very slow because it needs to dump all the new osd
  network ping stats [2] for some tasks, this can be bad especially when
  the cluster has large number of osds.

  Since these kind osd network ping stats doesn't need to be exposed to the python mgr module.
  so, it only makes the mgr doing more work than it needs to, it could cause the mgr slow or even hang and could cause the cpu usage of mgr process constantly high. the fix is to disable the ping time dump for those mgr python modules.

  The major fix from upstream is here [3], and also I found an
  improvement commit [4] that submitted later in another PR.

  We need to backport them to bionic Luminous and Mimic(Stein), Nautilus
  and Octopus have the fix

  [1] https://github.com/ceph/ceph/pull/28755
  [2] https://github.com/ceph/ceph/pull/28755/files#diff-5498d83111f1210998ee186e98d5836d2bce9992be7648addc83f59e798cddd8L430
  [3] https://github.com/ceph/ceph/pull/32406
  [4] https://github.com/ceph/ceph/pull/32554/commits/1112584621016c4a8cac1bedb1a1b8b17c394f7f

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