Re: [Xen-users] Use of memory on Dom0 ?

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Fri, Feb 12, 2010 at 12:03 AM, Olivier B. <xen.list@xxxxxxxxx> wrote:
>> Linux uses available memory for cache. If your application only use
>> 1000M, then the rest (800M) will be used for caching. That 800M can be
>> ballooned-down safely.
>>
>> If your application always need 1800M, then you should assign more
>> memory from the start.
>>
>>
>
> Ok, the problem is that it's not "my application", it's users's
> applications, I don't really control what they do with their DomU.

... but they gave you their requirements, right? "Give me a server
with 2G RAM" (or something like that). If yes, then you're only
obligated to give them that much resource. If you give them extra, and
then take it back later, and the process cause some apps not to work,
then it means the requirement is not valid anymore. They need to
request more resource.

Anyway, most apps (like LAMP) should be able to use swap.
The one time I got problem was with Oracle DB (it was a long time ago,
on Oracle 10g) when I shrunk domU memory lower than its SGA :P

>
> If I use file backend for a partition, will it use the Dom0 memory for read
> cache ? (if Xen doesn't open files in O_DIRECT mode...)

Sure. If you don't mind possible data corruption with file:/.

-- 
Fajar

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