[clug] Why virtual x86 machines?

[Andrew Donnellan]

On Fri, 21 Aug 2020 at 23:46, Hugh Fisher via linux <linux at lists.samba.org>
wrote:

> If a machine is idling away happily, so what? Why do we think it
> worthwhile or necessary to reach a level of utilization?
>

You correctly identify "monetary reasons". For rather obvious reasons, the
industry does indeed choose to have more money rather than choosing to have
less money.


> The alternative is demonstrated by my phone. Like most people I have a
>
Ghz CPU with gigabytes of RAM and storage in my pocket. It's idle a
> lot of the time, but I don't feel at all guilty about this because
> these phone computer systems are designed for irregular, varying
> workloads.
>
> Modern phones, which are mostly running Linux and the rest a variant
> of BSD Unix, can switch into and out of low power mode in fractions of
> a second. The OS can switch on or off individual hardware units within
> each chip. This doesn't stop them from being extremely fast: current
> generation ARM CPUs in phones have single threaded performance
> comparable or better than many Intel CPUs, and multithreaded isn't
> bad.
>
> I'm really curious as to why similar technology isn't being used in
> data centres. (Or if it is, why we don't hear more about it.)


Every modern high performance CPU has various advanced power management
capabilities, capable of sending various parts of the chip into different
levels of sleep state. The reason you don't hear more about it is that it's
so ubiquitous that it's impossible to buy a CPU that can't do that.

Power management doesn't address the capital cost of hardware, or the
operational limits of rack space, networking equipment, etc etc etc.

-- 
Andrew Donnellan
http://andrew.donnellan.id.au         andrew at donnellan.id.au