Re: [Lhns-devel] Re: Who's doing what with cpu/memory/node hotplug?

Matthias Fouquet-Lapar
2004-05-17T08:38:49Z

> In the ppc64 case, there is some partitioning that can be done of a
> large system. CPU hotplug lets us balance cpu power between
> partitions. You can also buy a machine with 32 cpus, but only have 16
> of them turned on. There's a switch you can flip to get more horsepower
> only when you need it. (for a price, of course)
>
> There's a quick mention of failure recovery here:
> http://www-1.ibm.com/servers/eserver/pseries/hardware/whitepapers/lpar_3.html
>
> But, the story on ppc64 is pretty much that the firmware detects the
> kinds of hardware failures that we handle, Linux is just notified of it
> afterword.

I think I'm not quite sure why you need hotplug to balance CPUs between
partitons. (You are not moving physical components for this, right ?)

> Remember, chips designs like the POWER4 tend to have a lot of cost and
> design overhead in error correction and detection that are quite absent
> from consumer type cpus.

Taken beside which CPU architecture has best the RAS features :-), which are
CPU error types on ppc64 (besides cache SBE etc) which allow gracefully
recovery (i.e. the OS continues operating and non-affected user processes
continue to run) and hotplug replacement

Thanks

Matthias Fouquet-Lapar Core Platform Software mfl@sgi.com VNET 521-8213
Principal Engineer Silicon Graphics Home Office (+33) 1 3047 4127