I report my  questions in a different way (in the first question i did a mistake):


1) I don't understand the means of set_membind() function. Why I should to allocate in a node "near" my cpuset and not in my local node (where thread or process runs?)

2) Which is the behaviour of HWLOC_MEMBIND_BIND  flag? 

From the manual:

"Allocate memory on the specified nodes."

It means that I can allocate without binding the memory? What happens if one thread allocate and another thread in another node  read/write for the first time this memory? In a little example I see the memory is allocated on the second thread, not where first thread does malloc().  So, when I have to use HWLOC_MEMBIND_BIND flag? Or it has nothing to do with binding?

If the effective allocation is done when first thread touch the memory, which is the means of this flag?


2) My goal is to replicate the behaviour of set_area_membind_nodeset() in some manner for all futures allocation without call this function each time I allocate some memory. Is it possible to do this?


Thanks.

2011/9/22 Gabriele Fatigati <g.fatigati@cineca.it>
Hi,

some questions:

1) I don't understand the means of HWLOC_MEMBIND_BIND policy. Why I should to allocate in a node "near" my cpuset and not in my local node ( where thread or process runs?)


2) My goal is to replicate the behaviour of set_area_membind_nodeset() in some manner for all futures allocation without call this function each time I allocate some memory. Is it possible to do this?



2011/9/22 Brice Goglin <Brice.Goglin@inria.fr>
Le 22/09/2011 12:20, Gabriele Fatigati a écrit :
> NUMA node(s) near the specified cpuset.
>
> What does   "nodes near the specified cpuset" means? The node wherethe
> specified cpuset lives?
> Set the default memory binding policy of the current process or thread
> to prefer the

The node near the CPU specified in the cpuset.

> The first thread allocates with a malloc an array. The second thread
> (bound on other node) initialize the array.
>
> The free memory on the nodes decrease only on the node where the
> second thread is. Is it rigth?

Yes.

>
>  hwloc_set_membind involves all future allocations?
>

Yes. And already allocated pages if you add the migrate flag.

Brice

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--
Ing. Gabriele Fatigati

HPC specialist

SuperComputing Applications and Innovation Department

Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy

www.cineca.it                    Tel:   +39 051 6171722

g.fatigati [AT] cineca.it          



--
Ing. Gabriele Fatigati

HPC specialist

SuperComputing Applications and Innovation Department

Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy

www.cineca.it                    Tel:   +39 051 6171722

g.fatigati [AT] cineca.it