Re: difference between this and that

On Mon, Mar 17, 2008 at 08:52:39PM -0400, Chuck Robey wrote:
I was giving some thought recently, to the trend towards adding more and
more cores to a single chip, and wondering if maybe, in the next years
ahead, if we wouldn't be seeing things that sound loony today, like a 4096
core motherboard.

Actually, there was a bit of a side-thread about this sort of thing on
the CVS mailing lists a couple of weeks ago. Definitely lots of cores
per system are on the way. You can buy a system with 64 hardware
threads from Sun today. A 128-thread system (dual T-2) will arrive
RSN and Sun have said they intend to double the threads-per-chip every
year. 4096 cores is still a way off and it's not currently clear what
will drive these sort of systems into the mainstream.

One problem is that FreeBSD currently assumes that a CPU mask will fit
into a long - this limits FreeBSD to 32 cores on arm/i386/ppc and 64
cores elsewhere. Getting rid of this limit is going to take some work.

With this in mind, could I ask for a little bit of discussion on the
differences between the SMP management that FreeBAD, and several other OSes
perform, and the things that stuff like Ganglia

As a simplification and if you consider that SMP systems are moving to
NUMA, the difference is mainly a matter of scale: There is an
additional knee in the cost of process migration and RAM access
between different CPU cores depending on whether they are on the same
chip, different chips within the same host or different hosts.

--
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.

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