[libvirt] [PATCH 1/3] add percentage limit parse and define support for RAM filesystems

[Eric Blake]

On 12/05/2013 06:17 AM, Daniel P. Berrange wrote:
> On Thu, Dec 05, 2013 at 06:12:22AM -0700, Eric Blake wrote:
>> On 12/05/2013 04:56 AM, Daniel P. Berrange wrote:
>>
>>>>>>>
>>>>>>> This patch enables percentage limit for ram filesystem
>>>>>>>
>>>>>>> <filesystem type='ram'>
>>>>>>>     <source usage='10%'/>
>>>>>>>     <target dir='/mnt'/>
>>>>>>> </filesystem>
>>>>>>>
>>

> 
> We do have APIs for querying host RAM, but if we wanted this, which I
> don't think we do, then tmpfs RAM % would want to be relative to guest
> RAM allocation not host RAM.

Ah - if you make that argument, then I agree - a management tool can
always calculate a percentage of guest-visible RAM.

> It doesn't make sense to have guest XML
> whose semantics differ according to the host environment - they should
> be self-contained.

Right - if we ever supported live migration, changing guest-visible
attributes during the migration is a non-starter.  So the XML must not
be tied to host percentage, at which point I don't see a reason for
supporting percentage in the XML.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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