Re: [Xen-devel] [PATCH] docs: improve documentation for the the dom0_mem command line option

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.03.12 at 12:24, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Wed, 2012-03-21 at 11:08 +0000, David Vrabel wrote:
>> +Set the amount of memory for the initial domain (dom0). If a size is
>> +positive, it represents an absolute value.  If a size is negative, the
>> +size specified is subtracted from the total available memory.
>>  
>> -* `min:<value>` specifies the minimum amount of memory allocated to dom0.
>> -* `max:<value>` specifies the maximum amount of memory allocated to dom0.
>> -* `<value>` specified the exact amount of memory allocated to dom0.
>> +* `min:<size>` specifies the minimum amount of memory allocated to dom0.
>> +* `max:<size>` specifies the maximum amount of memory allocated to dom0.
> 
> This means "max:<size> => min(<size>,<actual-host-ram>)" and min vice
> versa, right?
> 
> Or does min fail/panic if host-ram less than the given size?

It would likely panic in that case, as it would try to allocate as much
as was available when the allocation size was calculated, and that
size could have been slightly off wrt what is available at the point
the allocation is actually done.

>> +* `<size>` specified the exact amount of memory allocated to dom0.
> 
>               specifies
> 
> If you give both min: and max: but not this which takes precedence?

nr = min(max(<nr>, <min>), <max>, <avail>)

(But I think it really ought to be

nr = max(min(<nr>, <max>, <avail>), <min>)

i.e. honor the specified minimum even if less memory is available.
And of course <max> < <min> should get a defined treatment
too.)

Jan


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