[I reply to myself because I was replying half on two distinct threads]
On Sat, Apr 18, 2009 at 01:59:03PM +0200, tlaro...@polynum.com wrote:
>
> But my gut feeling, after reading about Mach or reading A. Tanenbaum
> (that I find poor---but he is A. Tanenbaum, I'm only T. Laronde),
> is that a cluster is above the OS (a collection of CPUs), but a
> NUMA is for the OS an atom, i.e. is below the OS, a kind of
> "processor", a single CPU (so NUMA without a strong hardware specifity
> is something I don't understand).
>
> In all the mathematical or computer work I have done, defining the
> element, the atom (that is the unit I don't have to know or to deal with
> what is inside) has always given the best results.
The link between this and the process migration is that, IMHO or in my
limited mind, one allocates, depending on resources available at the
moment, once and for the process duration, a node. This is OS business
: allocating resources from a cluster of CPUs.
The task doesn't migrate between nodes, it can migrate "inside"
the node, from core to core in a tightly memory space coupled CPU
(a mainframe, whether NUMA or not) that handles failover etc. But
this is infra-OS, "hardware" stuff and as far as the OS is concerned
nothing has changed since the node is an unit, an atom. And trying
to solve the problem by breaking the border (going inside the atom)
is something I don't feel.
--
Thierry Laronde (Alceste) <tlaronde +AT+ polynum +dot+ com>
http://www.kergis.com/
Key fingerprint = 0FF7 E906 FBAF FE95 FD89 250D 52B1 AE95 6006 F40C
