Re: memory size inside domU less than memory in domU config

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jun 20, 2011 at 06:55:04PM +0400, Vasiliy G Tolstov wrote:
> On Mon, 2011-06-20 at 10:36 -0400, Konrad Rzeszutek Wilk wrote:
> 
> > So I tried the same experiment - a physical machine with 'mem=1G' provided
> > and an PV guest with 'mem=1G'. The same exact kernel in both cases and got:
> > 
> > Machine with 'mem=1G' on the command line.
> > [    0.000000] Memory: 1022756k/1048576k available (5851k kernel code, 452k absent, 25368k reserved, 2881k data, 688k init)
> > 
> > PV guest:
> > [    0.000000] Memory: 1018888k/1048576k available (5851k kernel code, 448k absent, 29240k reserved, 2881k data, 688k init)
> > 
> > So a DomU guest "eats" an extra 4MB compared to running it under baremetal.
> > (Note, the DomU guest has no balloon space in this example).
> > 
> > The memblock=debug does provide the info of what the "other" reserved regions are
> > and it looks to be the matter of just going through the numbers to figure out what
> > it is.
> > 
> 
> Can You provide pv kernel cmdline and config file ?

kernel="/home/konrad/ssd/xtt/dist/common/vmlinuz"
extra="console=hvc0 debug earlyprintk=xenboot memblock=debug mem=1G"
memory=1024
maxmem=1024
vcpus=1
name="latest"
on_crash="preserve"
vfb = [ 'vnc=1, vnclisten=0.0.0.0,vncunused=1']
disk = ['phy:/dev/vg_guest_1/data-xfs,xvda,w']

And for the baremetal:

DISPLAY menu.txt
SERIAL 0 115200
PROMPT 5
TIMEOUT 20
DEFAULT BAREMETAL


MENU TITLE Bootable Options:
LABEL Local
	MENU LABEL Local
	KERNEL chain.c32
	APPEND hd0

LABEL BAREMETAL
   KERNEL vmlinuz
   APPEND mem=1G debug selinux=0 earlyprintk=serial console=ttyS0,115200 initcall_debug loglevel=10 memblock=debug