20 Jun
2011
20 Jun
'11
12:24 p.m.
On 20/06/11 14:13, Andy Smith wrote:
Hi OM,
Thanks for looking into this.
No problem.
On Mon, Jun 20, 2011 at 02:01:00PM +0200, Ole-Morten
Duesund wrote:
Yes they do. I have some that run on Xen 3.2.1 and some that run on Xen
4.0.1.
The ones that run under 3.2.1 are apparently missing more memory than
the ones that run on 4.0.1. One VM with 1024MB assigned memory running
under linux 2.6.32-bpo.5-amd under xen 3.2.1 reports 999MB with "free
-m". A similar VM with 1024MB assigned and running linux
2.6.32-5-xen-amd64 under 4.0.1 reports 1019MB with "free -m". Obviously
something is different, but I'm not entirely clear on the differences
between pvops and xen-kernels vs. Xen3.2 and Xen4.
I don't know exactly where the memory goes,
but on my 32-bit VMs
boot-time reported HIGHMEM + LOWMEM equals the amount of assigned memory,
so the "missing" memory seems to be linux-kernel overhead somewhere. My
64-bit VMs obviously don't show HIGHMEM and LOWMEM, but the "BIOS-provided
physical RAM map:" seems to fit nicely with the assigned memory.
Do your 64-bit VMs exhibit this issue at all? Someone running Debian wheezy (testing) has reported a
240M VM
missing almost 60M! And their HighTotal in /proc/meminfo has wrapped
over:
HighTotal: 4294959104 kB
so that looks quite broken.
Someone needs to report a bug to Debian about that if it hasn't been
already, and it'd also be nice to know if it goes away with 64-bit.
I haven't seen anything like this in 64-bit mode. (But then again, I
haven't seen anything like this in 32-bit mode either)
- OM