RE: [Xen-devel] pre-reservation of memory for domain creation

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

Jan Beulich wrote:
>>>> "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx> 14.01.10 08:19 >>>
>>    Currently guest initialization process in xend
>> (XendDomainInfo.py) is: 
>> 
>>    _constructDomain() --> domain_create() --> domain_max_vcpus() ...
>>    --> _initDomain() --> shadow_mem_control() ...
> 
> While the patch certainly matches what I had in mind, with this
> sequence 
> it is clear that the tools still will need adjustment: The full
> ballooning only happens from _initDomain(), and hence the
> pre-reservation (from _constructDomain) of 4Mb would still be too
> small for large vCPU counts. 

The pre-reservation of memory size should be no relationship with vcpu number. 
As vcpu hasn't been initialized at that point. On vcpu initialization, the 
patch has ballooned the shadow size to 128 pages per vcpu. Did you find some 
piece of code that use the pre-reserved memory to allocate vcpu-related memory? 

Thanks!
Dongxiao

> 
> I wonder though what all this memory is needed for before the domain
> (not to speak of secondary CPUs) actually gets started. If that could
> be 
> got under control, tools side adjustment would not be necessary. Tim?
> 
> Jan
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