Re: [Qemu-devel] Memory: how to determine the max memory size of one VM?

["Andreas Färber" <afaerber@suse.de>]

Am 10.02.2012 12:23, schrieb Zhi Yong Wu:
> On Fri, Feb 10, 2012 at 7:10 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
>> On Fri, Feb 10, 2012 at 11:00 AM, Zhi Yong Wu <zwu.kernel@gmail.com> wrote:
>>> On Fri, Feb 10, 2012 at 6:35 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
>>>> On Fri, Feb 10, 2012 at 9:47 AM, Zhi Yong Wu <zwu.kernel@gmail.com> wrote:
>>>>> Today i tried to create one VM with the option "-m 4000", and found it
>>>>> failed with the following errors:
>>>>>
>>>>> Failed to allocate 4194304000 B: Cannot allocate memory
>>>>> Aborted (core dumped)
>>>>
>>>> Did you run on a 32-bit host?
>>> No, it is one x86_64 host.
>>
>> That is weird.  Have you tried strace(1) to find out which system call
>> is failing and why?
> It seems that it failed to call mmap().  ENOMEM

/etc/sysconfig/ulimit on SUSE has a default SOFTVIRTUALLIMIT value of
"80", i.e. 80% of the available physical + swap memory can be allocated
by one process.
For our SLES use cases we applied a simple patch to raise this limit via
RLIMIT_AS (so that, e.g., a 24 GB RAM host can create VMs > -m 20G).

ulimit -Sv can change this value, too.

For upstream QEMU we felt setting proper limits is the responsibility of
a management tool.

Andreas

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