Yeah, I think that's the right solution. We'll have to check the impact on the
rest of the code, but I -think- it will be okay - else we'll have to make some
tweaks here and there. Either way, it's still the right answer, I think.
On Feb 9, 2012, at 6:14 AM, Jeff Squyres wrote:
> Should we just do this, then:
>
> Index: mca/hwloc/base/hwloc_base_util.c
> ===================================================================
> --- mca/hwloc/base/hwloc_base_util.c (revision 25885)
> +++ mca/hwloc/base/hwloc_base_util.c (working copy)
> @@ -173,6 +173,9 @@
> "hwloc:base:get_topology"));
>
> if (0 != hwloc_topology_init(&opal_hwloc_topology) ||
> + 0 != hwloc_topology_set_flags(opal_hwloc_topology,
> + (HWLOC_TOPOLOGY_FLAG_WHOLE_SYSTEM |
> + HWLOC_TOPOLOGY_FLAG_WHOLE_IO)) ||
> 0 != hwloc_topology_load(opal_hwloc_topology)) {
> return OPAL_ERR_NOT_SUPPORTED;
> }
>
>
>
> On Feb 9, 2012, at 8:04 AM, Ralph Castain wrote:
>
>> Yes, I missed that point before - too early in the morning :-/
>>
>> As I said in my last note, it would be nice to either have a flag indicating
>> we are bound, or see all the cpu info so we can compute that we are bound.
>> Either way, we still need to have a complete picture of all I/O devices so
>> you can compute the distance.
>>
>>
>> On Feb 9, 2012, at 6:01 AM, [email protected] wrote:
>>
>>>
>>>
>>> [email protected] wrote on 02/09/2012 01:32:31 PM:
>>>
>>>> De : Ralph Castain <[email protected]>
>>>> A : Open MPI Developers <[email protected]>
>>>> Date : 02/09/2012 01:32 PM
>>>> Objet : Re: [OMPI devel] btl/openib: get_ib_dev_distance doesn't see
>>>> processes as bound if the job has been launched by srun
>>>> Envoyé par : [email protected]
>>>>
>>>> Hi Nadia
>>>>
>>>> I'm wondering what value there is in showing the full topology, or
>>>> using it in any of our components, if the process is restricted to a
>>>> specific set of cpus? Does it really help to know that there are
>>>> other cpus out there that are unreachable?
>>>
>>> Ralph,
>>>
>>> The intention here is not to show cpus that are unreachable, but to fix an
>>> issue we have at least in get_ib_dev_distance() in the openib btl.
>>>
>>> The problem is that if a process is restricted to a single CPU, the
>>> algorithm used in get_ib_dev_distance doesn't work at all:
>>> I have 2 ib interfaces on my victim (say mlx4_0 and mlx4_1), and I want the
>>> openib btl to select the one that is the closest to my rank.
>>>
>>> As I said in my first e-mail, here is what is done today:
>>> . opal_paffinity_base_get_processor_info() is called to get the number of
>>> logical processors (we get 1 due to the singleton cpuset)
>>> . we loop over that # of processors to check whether our process is bound
>>> to one of them. In our case the loop will be executed only once and we will
>>> never get the correct binding information.
>>> . if the process is bound actually get the distance to the device.
>>> in our case, the distance won't be computed and mlx4_0 will be seen
>>> as "equivalent" to mlx4_1 in terms of distances. This is what I definitely
>>> want to avoid.
>>>
>>> Regards,
>>> Nadia
>>>
>>>>
>>>> On Feb 9, 2012, at 5:15 AM, [email protected] wrote:
>>>>
>>>>
>>>>
>>>> [email protected] wrote on 02/09/2012 12:20:41 PM:
>>>>
>>>>> De : Brice Goglin <[email protected]>
>>>>> A : Open MPI Developers <[email protected]>
>>>>> Date : 02/09/2012 12:20 PM
>>>>> Objet : Re: [OMPI devel] btl/openib: get_ib_dev_distance doesn't see
>>>>> processes as bound if the job has been launched by srun
>>>>> Envoyé par : [email protected]
>>>>>
>>>>> By default, hwloc only shows what's inside the current cpuset. There's
>>>>> an option to show everything instead (topology flag).
>>>>
>>>> So may be using that flag inside
>>>> opal_paffinity_base_get_processor_info() would be a better fix than
>>>> the one I'm proposing in my patch.
>>>>
>>>> I found a bunch of other places where things are managed as in
>>>> get_ib_dev_distance().
>>>>
>>>> Just doing a grep in the sources, I could find:
>>>> . init_maffinity() in btl/sm/btl_sm.c
>>>> . vader_init_maffinity() in btl/vader/btl_vader.c
>>>> . get_ib_dev_distance() in btl/wv/btl_wv_component.c
>>>>
>>>> So I think the flag Brice is talking about should definitely be the fix.
>>>>
>>>> Regards,
>>>> Nadia
>>>>
>>>>>
>>>>> Brice
>>>>>
>>>>>
>>>>>
>>>>> Le 09/02/2012 12:18, Jeff Squyres a écrit :
>>>>>> Just so that I understand this better -- if a process is bound in
>>>>> a cpuset, will tools like hwloc's lstopo only show the Linux
>>>>> processors *in that cpuset*? I.e., does it not have any visibility
>>>>> of the processors outside of its cpuset?
>>>>>>
>>>>>>
>>>>>> On Jan 27, 2012, at 11:38 AM, nadia.derbey wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> If a job is launched using "srun --resv-ports --cpu_bind:..." and slurm
>>>>>>> is configured with:
>>>>>>> TaskPlugin=task/affinity
>>>>>>> TaskPluginParam=Cpusets
>>>>>>>
>>>>>>> each rank of that job is in a cpuset that contains a single CPU.
>>>>>>>
>>>>>>> Now, if we use carto on top of this, the following happens in
>>>>>>> get_ib_dev_distance() (in btl/openib/btl_openib_component.c):
>>>>>>> . opal_paffinity_base_get_processor_info() is called to get the
>>>>>>> number of logical processors (we get 1 due to the singleton cpuset)
>>>>>>> . we loop over that # of processors to check whether our process is
>>>>>>> bound to one of them. In our case the loop will be executed only
>>>>>>> once and we will never get the correct binding information.
>>>>>>> . if the process is bound actually get the distance to the device.
>>>>>>> in our case we won't execute that part of the code.
>>>>>>>
>>>>>>> The attached patch is a proposal to fix the issue.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Nadia
>>>>>>>
>>>> <get_ib_dev_distance.patch>_______________________________________________
>>>>>>> devel mailing list
>>>>>>> [email protected]
>>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>>>>>
>>>>>
>>>>> _______________________________________________
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>>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel_______________________________________________
>>> devel mailing list
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>>
>> _______________________________________________
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>
>
> --
> Jeff Squyres
> [email protected]
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