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Re: NetBSD Jails

On Tue, 19 May 2020 08:10:00 +0930
Brett Lymn <> wrote:

> On Sat, May 16, 2020 at 09:51:42AM +0100, Sad Clouds wrote:
> > 
> > Just look at how Solaris does it - it has Zones (aka Jails) and
> > LDOMs (Logical Domains) on SPARC. LDOMs seem to be a much better
> > way of partitioning OS instances versus something like VMware or
> > Xen.
> > 
>  almost but not quite. A SPARC LDOM is more of a hardware
> partitionig, cpu and memory are dedicated to the LDOM for its
> exclusive use.  You can configure some dynamism by allowing cpu to be
> added/removed automatically when the load average increases/decreases
> but this relies on the guest doing dynamic reconfiguration.

That's exactly what I was referring to. Yes this is specific to SPARC
where they have a very small firmware hypervisor. The advantage is how
hardware resources are dedicated to a specific domain, so the OS can
use them directly with very little overhead.

Xen supports "PCI passthrough", which can reduce the overheads when a
guest accesses that device. But I don't think it has anything like "CPU
or memory passthrough", it supports "CPU pinning" however I think you
still end up with excessive cache and TLBs thrashing.

I haven't actually done any detailed benchmarking at the hardware
level, so could be talking complete nonsense. This is just the
impression I got when reading various technical manuals over the last
few years.

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