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Subject: Re: [hwloc-users] Thread binding problem
From: Samuel Thibault (samuel.thibault_at_[hidden])
Date: 2012-09-06 04:44:57


Gabriele Fatigati, le Thu 06 Sep 2012 10:12:38 +0200, a écrit :
> mbind hwloc_linux_set_area_membind()  fails:
>
> Error from HWLOC mbind: Cannot allocate memory 

Ok. mbind is not really supposed to allocate much memory, but it still
does allocate some, to record the policy

> // hwloc_obj_t obj = hwloc_get_obj_by_type(topology, HWLOC_OBJ_NODE, tid);
> hwloc_obj_t obj = hwloc_get_obj_by_type(topology, HWLOC_OBJ_PU, tid);
> hwloc_cpuset_t cpuset = hwloc_bitmap_dup(obj->cpuset);
> hwloc_bitmap_singlify(cpuset);
> hwloc_set_cpubind(topology, cpuset, HWLOC_CPUBIND_THREAD);
>
> for( i = chunk*tid; i < len; i+=PAGE_SIZE) {
> // res = hwloc_set_area_membind_nodeset(topology, &array[i], PAGE_SIZE, obj->nodeset, HWLOC_MEMBIND_BIND, HWLOC_MEMBIND_THREAD);
> res = hwloc_set_area_membind(topology, &array[i], PAGE_SIZE, cpuset, HWLOC_MEMBIND_BIND, HWLOC_MEMBIND_THREAD);

and I'm afraid that calling set_area_membind for each page might be too
dense: the kernel is probably allocating a memory policy record for each
page, not being able to merge adjacent equal policies.

You could check in /proc/meminfo which number goes high, it's probably
in-kernel data, such as the Slab.

Samuel