On 30-set-09, at 09:29, Samuel Thibault wrote:
Hello,
Hi Samuel,
Fawzi Mohamed, le Wed 30 Sep 2009 09:16:36 +0200, a écrit :
1) a fully hierarchical representation of the machine/hardware
where each level
is a partition, and each level fully covers the previous one (from
any node you
go through all levels using father/childrens, father/child are just
one level
away from each other.
This is basically what is there now.
2) outside the hierarchy 1 (but built using its object, probably
the NUMA
nodes) there will be
2.1) maybe the full connection graph
2.2) a hierarchical view of it, like the lgroups, where the levels
are not
necessarily a partition, and that could also refer not to the
sublevel, but
directly to lower levels. Going up the hierarchy you get the next
neighbors.
Err, no, in our plans 2.2 was in 1) already, and levels are thus still
partitions, but somehow arbitrary ones, according to heuristics
based on
the graph. Isn't that the case with lgroups ? (I haven't ever had
access
to a solaris numa machine)
If you look at the example described in the document that I had linked
http://opensolaris.org/os/community/performance/mpo_overview.pdf
you see the that for a ring topology some level (that you always get
adding the next neighbors) do not form a partition (i.e. they
overlap), such an overlap unavoidable if to build the next higher
hierarchy you simply add the next neighbors.
Having a partition is very useful when, for instance instead of
looking for a resource you want to restrict/pin a thread, for this
reasons there are psets and lpls (lgroup partition loads, intersection
of lgrops and processor partition, which are again a partition), and
both are used on opensolaris.
Well you don't have to mirror what solaris does, but I found that
quite nice, so I was thinking you wanted to go in that direction.
For a the ring topology a-b-c-d-a is difficult to find a good
partition... and having both partition and non partition views (one
used for resource allocation/distribution, the other for resource
finding/stealing), is quite clean imho.
ciao
Fawzi
