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Subject: Re: [hwloc-users] Thread binding problem
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2012-09-06 05:02:54


Le 06/09/2012 10:44, Samuel Thibault a écrit :
> 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.
>

It's supposed to merge VMA with same policies (from what I understand in
the code), but I don't know if that actually works.
Maybe Gabriele found a kernel bug :)

Brice