[Mavrick] SRU: Set maximum of domain visible memory to 70G

[Stefan Bader]

On 12/10/2010 03:52 PM, Tim Gardner wrote:
> On 12/10/2010 07:10 AM, Stefan Bader wrote:
>> SRU justification:
>>
>> Impact: The config option XEN_MAX_DOMAIN_MEMORY controls how much memory
>> a Xen instance is seeing. The default for 64bit is 32GB, which is the
>> reason that m2.4xlarge instances only report this amount of memory.
>>
>> Fix: Setting this limit to 70GB as there is a known restriction for
>> t1.micro instances at about 80GB.
>>
>> Testcase: Booted m2.4xlarge with this set to 32GB shows 32GB of memory,
>> when set to 70GB, it correctly reports 68GB. Booted a t1.micro as well
>> to verify this has not caused problems there.
>>
>>  From c72705539ee164cdd100570c1340887f81a63d98 Mon Sep 17 00:00:00 2001
>> From: Stefan Bader<stefan.bader at canonical.com>
>> Date: Thu, 9 Dec 2010 17:59:36 +0100
>> Subject: [PATCH] UBUNTU: Set maximum of domain visible memory to 70G
>>
>> BugLink: http://bugs.launchpad.net/bugs/667796
>>
>> Otherwise the largest instances will be stuck with 32G of memory. 70G
>> was chosen as there are some known problems on small instances around
>> 80GB and the largest instance is using 68GB.
>>
>> Signed-off-by: Stefan Bader<stefan.bader at canonical.com>
>> ---
>>   debian.master/config/config.common.ubuntu |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/debian.master/config/config.common.ubuntu
>> b/debian.master/config/config.common.ubuntu
>> index b0c486b..ed8ad01 100644
>> --- a/debian.master/config/config.common.ubuntu
>> +++ b/debian.master/config/config.common.ubuntu
>> @@ -5014,7 +5014,7 @@ CONFIG_XEN_COMPAT_XENFS=y
>>   CONFIG_XEN_DEV_EVTCHN=m
>>   CONFIG_XEN_FBDEV_FRONTEND=m
>>   CONFIG_XEN_KBDDEV_FRONTEND=m
>> -CONFIG_XEN_MAX_DOMAIN_MEMORY=32
>> +CONFIG_XEN_MAX_DOMAIN_MEMORY=70
>>   CONFIG_XEN_SAVE_RESTORE=y
>>   CONFIG_XEN_SCRUB_PAGES=y
>>   CONFIG_XEN_SYS_HYPERVISOR=y
> 
> Any thoughts on the impact this change will have on -generic and
> -server? Perhaps we should restrict this change to the -ec2 flavour only.
> 
> rtg

As far as I understand it, this value is only used in the xen mmu code when
setting up domU. The comment there says, it is in that case using a page per GB.
But as we have the virtual flavour, it probably makes sense to use it.

-Stefan