[Xen-devel] balloon driver and mem parameter

[Matthieu PATOU <matxen@xxxxxxxxx>]

Hello all
in december on this list keir told me that in order to be able to grow memory in
 a domain above the initial allocation i have to put a mem parameter in my
kernel command line.
Well first of all adding this is not trivial:
i use sxp configuration files, so i try to add a subsection (mem "65536") in the
linux subsection. The creation of the domain was ok but the Kernel command line
(from DMESG) didn't show the parameter not great ... 
I 've try several other things that failed to ... the only solution i find was
to cheat with the root parameter of my config file.
So instead of having this line 
(root '/dev/hdb1 ro')
i change to have :
(root '/dev/hdb1 ro mem=65536')

By doing this i manage to have domU to see my parameter but it doesn't seems to
care because (with an initial memory of 32Mo) i have this report :
32MB LOWMEM available.
  HighMem zone: 0 pages, LIFO batch:1
Kernel command line:  ip=off root=/dev/hdb1 ro mem=65536
Memory: 29976k/32768k available (1752k kernel code, 2744k reserved, 370k data,
96k init, 0k highmem) 

So ...
what can i do to transmit the mem parameter cleanly, what can i do to make domU
see that its memory is 65536.
By the way, is there a simple way to test the memory allocation (suppose that i
started a domain with 32 Mo and i grow it to 64Mo, free will still show 64Mo so
is there a simple solution to test it ... for instance writing a program that
allocate 20Mo via a big malloc call and start it twice if it runs twice and
there is no swap so it means that there is more than 32 Mo available)
For Dom0 what can be done ?
For the moment i start with a quite huge dom0_memory parameter and at the
startup reduce it with xm balloon 32M (i've done it in a startup script).

Regards
Matthieu


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