[Xen-users] memory=x & maxmem=y

[Paul Archer <tigger@xxxxxx>]

I have been playing with memory= and maxmem=, but I'm not seeing what I 
think I should be seeing, namely that the memory available to a domU can be 
increased on the fly.
For example, I have:
memory = 256
maxmem = 512
in my config file.

I can run 'xm mem-set mydomain 128', and the memory in the domU will drop to 
128. I can run 'xm mem-set mydomain 256' and bring it back up to its 
original memory level. But if I run 'xm mem-set mydomain 512', then 'xm 
list' will see 512M allocated to the domain, but the domain will only see 
256M. However, if I 'reboot' the domU, when it comes back up, it will have 
512M of memory.
According to Jayson Vantuyl in a discussion on this list a few days ago:
"For example, if you have these options for a domain:

memory=1024
maxmem=4096

You will have the kernel boot up with 1GB of memory.  At any point you can 
increase it to, for example, 2 GB with this command:
xm mem-set <domain> 2048

The kernel will automagically increase to 2GB of RAM.  This is, as you might 
imagine, extremely cool."
Is this true? Is it possible to set the initial memory level to be something 
less than maxmem, and have the running (linux) domU see the new memory level 
when it is increased? If so, then is there something I'm missing in my 
setup? A driver in dom0 or domU, perhaps?
Paul Archer



--------------------------------------------------------------
"I'll say this about Linux: it's the first time I've seen Unix 
on the right platform."--Steve Ballmer, president of Microsoft
(NB: Microsoft used to own SCO, which did, and still does,
produce a Unix for the Intel platform.)
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