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Subject: Re: [OMPI devel] [OMPI users] huge VmRSS on rank 0 after MPI_Init when using "btl_openib_receive_queues" option
From: Eloi Gaudry (eg_at_[hidden])
Date: 2011-07-13 03:16:11


Unfortunately, I could not observe such a VmRSS increase.

Here is the command line used to perform this test:
/opt/openmpi-1.4.2/bin/mpirun -np 256 --hostfile host.list --display-map
--mca mpi_warn_on_fork 0 --mca btl_openib_want_fork_support 0 --mca btl
openib,sm,self --mca btl_openib_receive_queues P,32768,128,96,64 --mca
btl_openib_max_send_size 32768 --mca btl_openib_eager_limit 32768 --mca
btl_openib_rndv_eager_limit 32768 $HOME/info_mp

and the outputs from rank 0 and rank 255 (the root of the 1-byte
MPI_Gather):
[hbn0170: 0/256] Allgather with one byte to process with rank 255 (VmRSS:
1343463424bytes)
[hbn0170: 0/256] Done Allgather with one byte to process with rank 255
(VmRSS: 1343488000bytes)

[hbn0232: 255/256] Allgather with one byte to process with rank 255
(VmRSS: 261124096bytes)
[hbn0232: 255/256] Done Allgather with one byte to process with rank 255
(VmRSS: 288129024bytes)

note that 256*128*(96+64+32768)=1340108800 bytes and it matches the VmRSS
observed on proc 0.

éloi

On Sat, 09 Jul 2011 13:13:04 +0200, Jeff Squyres <jsquyres_at_[hidden]>
wrote:

> Sorry for the delayed reply.
>
> I'm guessing that there's some kind of rooted collective operation
> occurring during MPI_INIT. Try doing a 1 byte MPI_GATHER to another
> rank in MCW (e.g., to rank 5) and see if the VmSS goes to the same size
> as MCW rank 0.
>
>
> On Jul 8, 2011, at 5:17 AM, Eloi Gaudry wrote:
>
>> what i cannot understand is the reason why this extra memory would be
>> initialized on proc 0 only.
>> as far as i know, this doesn't make sense.
>> éloi
>>
>>> On 22/04/2011 08:52, Eloi Gaudry wrote:
>>>> it varies with the receive_queues specification *and* with the number
>>>> of mpi processes: memory_consumed = nb_mpi_process * nb_buffers *
>>>> (buffer_size + low_buffer_count_watermark + credit_window_size )
>>>>
>>>> éloi
>>>>
>>>>
>>>> On 04/22/2011 12:26 AM, Jeff Squyres wrote:
>>>>> Does it vary exactly according to your receive_queues specification?
>>>>>
>>>>> On Apr 19, 2011, at 9:03 AM, Eloi Gaudry wrote:
>>>>>
>>>>>> hello,
>>>>>>
>>>>>> i would like to get your input on this:
>>>>>> when launching a parallel computation on 128 nodes using openib and
>>>>>> the "-mca btl_openib_receive_queues P,65536,256,192,128" option, i
>>>>>> observe a rather large resident memory consumption (2GB:
>>>>>> 65336*256*128) on the process with rank 0 (and only this process)
>>>>>> just after a call to MPI_Init.
>>>>>>
>>>>>> i'd like to know why the other processes doesn't behave the same:
>>>>>> - other processes located on the same nodes don't use that amount
>>>>>> of memory
>>>>>> - all others processes (i.e. located on any other nodes) neither
>>>>>>
>>>>>> i'm using OpenMPI-1.4.2, built with gcc-4.3.4 and
>>>>>> '--enable-cxx-exceptions --with-pic --with-threads=posix' options.
>>>>>>
>>>>>> thanks for your help,
>>>>>> éloi
>>
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>

-- 
Eloi Gaudry
Senior Product Development Engineer
Free Field Technologies
Company Website: http://www.fft.be
Direct Phone Number: +32 10 495 147