Re: [Xen-devel] [PATCH 0 of 4] Handling of (some) low memory conditions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.02.12 at 15:40, "Andres Lagar-Cavilla" <andres@xxxxxxxxxxxxxxxx> 
>>> wrote:
>>>>> On 16.02.12 at 04:57, Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
>>>>> wrote:
>>> - Add a VIRQ that the hypervisor can emit when reaching a low memory
>>> threshold.
>>
>> In this patch, which didn't make it to my inbox yet, you will want to
>> change this
>>
>> +    if ( (total_avail_pages << PAGE_SHIFT) <= opt_low_mem_virq )
>>
>> to
>>
>>     if ( total_avail_pages <= PFN_DOWN(opt_low_mem_virq) )
>>
>> to avoid the case (on 32-bit hypervisors) where total_avail_pages,
>> being just 'long', would get significant bits shifted out.
>>
>> I'm further wondering whether the default value shouldn't be set
>> dynamically based on available memory and/or taking into account
>> an eventual dom0_mem= option.
> 
> I can cap or get rid of the threshold (and the virq) if it doesn't make
> sense with respect to total memory. I'm not sure about integrating
> dom0_mem, since dom0's footprint is also a quantity manipulated by the
> receiver of the virq.

No, dom0_mem= is only specifying the starting value, and the case
that would be of possibly interest is that of having a negative amount
specified.

Jan


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