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[Bug 1546159] Comment bridged from LTC Bugzilla

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Date: Thu, 28 Apr 2016 13:30:38 -0000
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------- Comment From hbathini@xxxxxxxxxx 2016-04-28 09:20 EDT-------
(In reply to comment #20)
> That patch (http://patchwork.ozlabs.org/patch/577193/) should have made it
> upstream by now. What is going on with it ?

Mahesh spoke to PPC Maintainer offline about this patch. Since the
changes are more invasive (and at the code path which is used at every
boot) review is taking time. Maintainer is also thinking about alternate
solution but that includes rewriting lots of cpu numbering code. So as
of now maintainer conveyed that he needs some more time (hasn't mention
specific time) to review this patch to be very sure that it is not
harmful.

So as it stands, this patch may not be going anywhere at least for some
time..

Thanks
Hari

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https://bugs.launchpad.net/bugs/1546159

Title:
  ISST-LTE: high cpus number need a high crashkernel value in kdump

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Xenial:
  In Progress

Bug description:
  ---Problem Description---
  The kdump kernel will be booted with "maxcpus=1", so no matter how many cpus this system has, only one cpu will be brought up during kdump I think. But on LPAR thymelp2, if we allocate 40 cpus on it, then kdump works just fine with 512M  as crashkernel value. But if we allocate 200 cpus on it, kdump fails by trggering OOM. It has been proved that in latter situation we need 1.5G RAM reserved for kdump to let it works.
   
  ---Steps to Reproduce---
   1. configure kdump with crashkernel=512M on thymelp2
  2. allcoate 40 cpus on thymelp2 and trigger kdump
  3. allocate 200 cpus on thymelp2 then do kdump again
   
  ---
  Mahesh has posted a patch upstream to provide support for nr_cpus in kdump kernel.
  That should take care of this problem..

  https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-February/138619.html
  ---

  Heads up Canonical: We'll want this patch included as soon
  possible/practical.

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