Re: [Xen-devel] a ton of kernel issues

[George Shuklin <george.shuklin@xxxxxxxxx>]

On 14.12.2011 11:47, Fajar A. Nugraha wrote:
> > Well... For us it make HUGE difference. We running cloud with very precise
> > accounting of  fast automaric memory allocation for customer's domains and
> > we account them for ... em... KiB*hr value, so if we account domains based
> > on xc.get_domain_memkb value and customers saw difference between TotalMem
> > and our values this will make them feel like we cheating. We not greedy and
> > ready to 'cut' our mem_kb value to their TotalMem, but I hasn't found any
> > formula for that (calculate TotalMem from static-max and dom_kb values) and
> > I can't trust any data from customer's domains (except request for memory we
> > accept, serve and happily take money for 'more memory').
> >
> > It sounds ridiculous, but we avoiding pv_ops kernels usage due that little
> > ~50Mb steal. We stuck with -xen kernels (forward porting from SUSE and
> > native CentOS 2.6.18-xen). I don't know what we will do in the future, but
> > right now PV-ops is not good...
> Why not just explain what really happened in a noob-friendly language?
>
> For example, when buying a computer with built-in graphic card,
> MemTotal is always lower than the ammount of memory actually
> installed. Yet a simple explanation "some of the memory is used by the
> built-in graphic card" is enough, without having to go into details of
> what is the formula to calculate how much memory actualy used.
Well, this is fine if we provide customers normal 'VDS-like' virtual 
machines. You getting 256MiB, some of it is used by kernel and not 
displayed as TotalMem. But we provide vm with ellastic memory (like 
256MiB - 8GiB) with promise 'we will serve you enough memory to your 
applications and you will pay only for allocated memory for your VM'. 
User expects we give him + 2GiB for 2 min and we charge him for 
2*2/60=0.066 GiB*hr. With -xen kernels they got exactly they paid (at 
least, with TotalMem value). If we saying them 'here something you don't 
understand' this will cause some doubts.


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