This is actually a standard Linux behaviour: to use more than 1GB RAM on x86,
you need to enable CONFIG_HIGHMEM_4G, regardless of whether it''s a Xen
guest
or a native kernel.
In a XenLinux src tree do:
make ARCH=xen menuconfig
The option you want is under X86 Processor Configuration -> High memory
support. Select 4GB and domains using that kernel will happily deal with
1-4GB of allocated RAM.
HTH,
Mark
On Monday 09 May 2005 15:39, JHJE (Jan Holst Jensen)
wrote:> Hi.
>
> I am a bit confused about the usage of memory above 1GB in Xen. I have
> two servers running Debian Sarge with Xen 2.0.5 installed on top of
> that. Both claim to have only 900 MB memory when booting Debian Sarge
> (not Xen) although both servers have 4 GB physical memory.
>
> My initial reaction was not to care, since I assumed that this was just
> a quirk of the stock Debian kernel. And it seems that when booting into
> Xen I can use all 4 GB, at least I can boot three domains with 1000 MB,
> 1500 MB mem and 1000 MB respectively:
>
> xen-test:/machines# xm list
> Name Id Mem(MB) CPU State Time(s) Console
> Domain-0 0 123 0 r---- 102.7
> debian-sarge 9 1000 1 -b--- 1.1 9609
> debian2-sarge 10 1500 0 -b--- 6.0 9610
> rh9-jhje 11 999 1 -b--- 6.1 9611
>
> However, even though "xm list" will report that a domU is
assigned 1500
> MB memory, when logging into the domain and doing "cat
/proc/meminfo" it
> only sees about 900 MB. This is regardless of whether I boot a 2.4 or
> 2.6 domU kernel:
>
> debian2-sarge:~# cat /proc/meminfo
> MemTotal: 904376 kB
> MemFree: 891328 kB
>
> Do I have to somehow tell the domU kernel the memory size as a boot
> parameter, or will I have to build my own domU kernels ?
>
> Cheers
> -- Jan Holst Jensen, Novo Nordisk A/S, Denmark
>
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