Re: [Qemu-devel] [REBASE PATCH v5 1/2] machine: add default_ram_size to machine class

[Alexander Graf]

> Am 30.04.2015 um 11:40 schrieb Thomas Huth <address@hidden>:
> 
> On Thu, 30 Apr 2015 11:18:05 +0200
> Alexander Graf <address@hidden> wrote:
> 
>> 
>> 
>>> On 30.04.15 06:41, Nikunj A Dadhania wrote:
>>> 
>>> Hi Paolo,
>>> 
>>> Paolo Bonzini <address@hidden> writes:
>>>> On 29/04/2015 11:06, Nikunj A Dadhania wrote:
>>>>>> so David can push both patches.
>>>>>> 
>>>>>> But isn't 1G a bit too much?  At least on x86 you can easily boot with 
>>>>>> 512M.
>>>>> 
>>>>> I understood this number as not the _minimum memory_ to boot the
>>>>> VM. And this will only come in picture when the user has not specified
>>>>> any memory.
>>>> 
>>>> This in turn will basically only happen for QEMU developers.  So keeping
>>>> the default on the low side would make sense.
>>>> 
>>>> On my (4G memory) laptop I might not even be able to boot a PPC64 VM
>>>> with 1G and TCG, but I can do that nicely with 256M.
>>> 
>>> That will be fine with me as well, i.e. 256M
>>> 
>>> David/Alex, Do you have comments on this before we change it?
>> 
>> I've seen RAM size combinations that seemed to work ok, but then failed
>> during grub2 execution for example. Please verify with all reasonably
>> realistically executed distributions that 256MB is enough.
> 
> Since this default value will likely be there for the next couple of
> years, it's maybe better to use a slightly higher value than one that
> is too low - the amount of RAM that a guest requires likely rather
> increases in the next years instead of going down again. So I think
> using 512 MB instead is maybe a good compromise?

Again, even with 512, please verify a few different distros and check that they 
run.

Alex