Re: [Qemu-devel] default guest RAM size?

[Anthony Liguori <anthony@codemonkey.ws>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On 5 March 2013 13:26, Michael Tokarev <mjt@tls.msk.ru> wrote:
>> For many years, qemu defaults to 128Mb of guest RAM size.
>> Today, this is just too small, and many OSes fails to boot
>> with this size, more, they fail to produce any reasonable
>> messages either (eg, windows7 just crashes at startup).
>
> If you make the default bigger then some boards will crash
> or behave weirdly because they try to map more RAM in than
> will fit into the space for RAM in their address maps.
>
>> Some distributions (eg ubuntu) had a local patch to increase
>> this value, for years.
>>
>> Maybe it's time to increase the default RAM size a bit?
>> Make it arch-specific if needs to be ?
>
> I tried two years ago to get a 'default RAM size' parameter

I don't see that in this series.  It's a maximum RAM size.

Anyway, there's no problem changing the default ram size (and making it
per-board).  The only requirement is that -M pc-1.4 and below continues
to expose 128MB as the default.

It's not worth bike shedding over what the default should be for pc
targets.  256 or 512 would be equally good defaults and either would be
acceptable.

Regards,

Anthony Liguori

> added to the QEMUMachine struct, but the patchseries got shot
> down because it didn't attempt to address NUMA / simulate
> the fact you can only add RAM one DIMM at a time / etc...
>
> http://lists.gnu.org/archive/html/qemu-devel/2011-03/msg02907.html
>
> -- PMM