Open Stack

> On Mon, Jul 02, 2018 at 07:32:13PM +0100, Dr. David Alan Gilbert wrote:
> > * Fox, Kevin M (Kevin.Fox at pnnl.gov) wrote:
> > > Can a stock kernel with all the probing still intact ever perform as well as a
> custom one with all the non relevant stuff stripped out? Subsecond pod starting
> is very handy.
> 
> I haven't benchmarked it.  What is the command-line to start a second
> container in the existing VM?  By default Kata launches a new VM.

I think Alan was saying 'boot times <1s', not 'a second boot', if I'm interpreting you both correctly...
  (an aside - afaik, you need to use k8s to launch a second container in a VM - that is two containers in a pod (sandbox in Kata). You cannot do this from Docker afaik).

>   initcall_debug
>   nr_cpus=4
>   ip=::::::<blob>::off::
> 
> initcall_debug is a strange one since it can slow things down by
> printing lots of output to the console.  I haven't measured how much
> difference it makes though.

Hah, I suspect initcall_debug is actually a hangover from measuring and trying to reduce boot-time. I suspect that one can go - but I've never measured if it makes a difference.

Whilst I'm here - one more thought for boot time - some time back I measured that booting with vcpus=2 is quicker than booting with vcpus=1 (my theory is the kernel can then parallelize the init call sequences for instance. And, in fact, iirc, vcpus=2 was the optimal, as if you add more vcpus they then take more time for initialization). I think we moved to having a default of vcpus=1 when we went to hotplug vcpus - it might be worth measuring and considering if a default of vcpus=2 gives us a boot win - but it will likely add a little complexity to the hotplug math (/cc Julio)

Graham

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