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Subject: Re: [OMPI users] Binding to Core Warning
From: Saliya Ekanayake (esaliya_at_[hidden])
Date: 2014-02-26 15:17:48


I have a followup question on this. In our application we have parallel for
loops similar to OMP parallel for. I noticed that in order to gain speedup
with threads I've to set --bind-to none, otherwise multiple threads will
bind to same core giving no increase in performance. For example, I get
following (attached) performance for a simple 3point stencil computation
run with T threads on 1 MPI process on 1 node (Tx1x1).

My understanding is even when there are multiple procs per node we should
use --bind-to none in order to get performance with threads. Is this
correct? Also, what's the disadvantage of not using --bind-to core?

Thank you,
Saliya

On Wed, Feb 26, 2014 at 11:01 AM, Saliya Ekanayake <esaliya_at_[hidden]>wrote:

> Thank you Ralph, I'll check this.
>
>
> On Wed, Feb 26, 2014 at 10:04 AM, Ralph Castain <rhc_at_[hidden]> wrote:
>
>> It means that OMPI didn't get built against libnuma, and so we can't
>> ensure that memory is being bound local to the proc binding. Check to see
>> if numactl and numactl-devel are installed, or you can turn off the warning
>> using "-mca hwloc_base_mem_bind_failure_action silent"
>>
>>
>> On Feb 25, 2014, at 10:32 PM, Saliya Ekanayake <esaliya_at_[hidden]> wrote:
>>
>> Hi,
>>
>> I tried to run an MPI Java program with --bind-to core. I receive the
>> following warning and wonder how to fix this.
>>
>>
>> WARNING: a request was made to bind a process. While the system
>> supports binding the process itself, at least one node does NOT
>> support binding memory to the process location.
>>
>> Node: 192.168.0.19
>>
>> This is a warning only; your job will continue, though performance may
>> be degraded.
>>
>>
>> Thank you,
>> Saliya
>>
>> --
>> Saliya Ekanayake esaliya_at_[hidden]
>> Cell 812-391-4914 Home 812-961-6383
>> http://saliya.org
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>
>
>
> --
> Saliya Ekanayake esaliya_at_[hidden]
> Cell 812-391-4914 Home 812-961-6383
> http://saliya.org
>

-- 
Saliya Ekanayake esaliya_at_[hidden]
Cell 812-391-4914 Home 812-961-6383
http://saliya.org



3pointstencil.png