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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.
 
Contact Information = Ping Tian Han/pthan@xxxxxxxxxx Carrie Mitsuyoshi/carriemi@xxxxxxxxxx 
 
---uname output---
Linux thymelp2 4.2.0-23-generic #28~14.04.1-Ubuntu SMP Thu Dec 31 13:41:19 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux
 
Machine Type = 8247-22L, LPAR 
 ---Debugger---
A debugger was configured, however the system did not enter into the debugger
 
---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
 
*Additional Instructions for Ping Tian Han/pthan@xxxxxxxxxx Carrie Mitsuyoshi/carriemi@xxxxxxxxxx: 
-Post a private note with access information to the machine that the bug is occuring on.

== Comment: #1 - Nadia N. Fry <nadiaf@xxxxxxxxxx> - 2016-02-19 13:53:02 ==
Any update?

== Comment: #2 - Hari Krishna Bathini <hbathini@xxxxxxxxxx> - 2016-02-22 03:40:05 ==
Mahesh posted a patch upstream which should take care of this problem

http://patchwork.ozlabs.org/patch/577193/

Thanks
Hari

** Affects: linux (Ubuntu)
     Importance: High
     Assignee: Canonical Kernel Team (canonical-kernel-team)
         Status: Triaged


** Tags: architecture-ppc64le bot-comment bugnameltc-137281 severity-high targetmilestone-inin---
-- 
ISST-LTE: pVM:high cpus number need a high crashkernel value in kdump
https://bugs.launchpad.net/bugs/1560552
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