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Re: [Xen-devel] xm mem-set causes kernel panic

To: "Krysan, Susan" <KRYSANS@xxxxxxxxxx>
Subject: Re: [Xen-devel] xm mem-set causes kernel panic
From: Andrew Theurer <habanero@xxxxxxxxxx>
Date: Wed, 03 May 2006 16:29:08 -0500
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>, "Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx>, "Vessey, Bruce A" <Bruce.Vessey@xxxxxxxxxx>, "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
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Krysan, Susan wrote:
We did run using unstable. We installed sles10 beta11 but we pulled and built 
xen-unstable changeset 9903 from xensource repository.  We have not tried with 
PAE hypervisor.  It is not our focus.  How desperately would you need us to try 
I have done this on 32GB x86_64 as well and have pretty much the same problem. I think the problem is that the static memory allocations in the kernel for things like mem_map, page_struct etc, are quite large for 32GB, and do not shrink (or do they?) when balooning to 512 MB. This leaves almost no usable memory when balooning down, and you get OOM. If you know you don't need 32G for dom0, I would try setting dom0_mem to something much lower, like 1GB.

-Andrew Theurer

Sue Krysan
Linux Systems Group
Unisys Corporation

-----Original Message-----
From: Ian Pratt [mailto:m+Ian.Pratt@xxxxxxxxxxxx]
Sent: Wednesday, May 03, 2006 4:19 PM
To: Krysan, Susan; xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Subrahmanian, Raj; Vessey, Bruce A; Puthiyaparambil, Aravindh; Carb,
Brian A; ian.pratt@xxxxxxxxxxxx
Subject: RE: [Xen-devel] xm mem-set causes kernel panic

When I boot the ES7000 with 32 GB of RAM, dom0 is allocated almost all of it. I issued an xm mem-set 0 512 command to decrease dom0's memory to 512 MB. Using xentop, I see the amount of memory allocated to dom0 slowly decrease. The kernel panic occurs when dom0's memory is around 1 GB. The serial console output is attached. Using SLES10 Beta 11 upgraded to xen changeset 9903.

Can you repro this on -unstable? What about with a PAE hypervisor?


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