[mvapich-discuss] Question about launch times with mpd

[Chris Worley]

Craig,

I've run into this before w/ authentication mechanisms... which is why
I always use local password files.

Specifically, I was using YP and YP scaling was so bad that ~2000
processes would cause ssh timeouts, and the job would die.

You're not seeing anything this bad, and I doubt you're using YP, but
try local password files (and like entries in /etc/nsswitch.conf).

Also, remove name server resolution too: everything in /etc/hosts, and
no resolve.conf.

Hope this helps,

Chris
On Mon, Jun 30, 2008 at 10:38 AM, Craig Tierney <Craig.Tierney at noaa.gov> wrote:
> Sorry to followup my own post, but I forget to provide
> a few bits of information:
>
> - This happens with mvapich2 1.0 and 1.0.2p1
> - I am running OFED 1.2.5.1 and Intel ifort/icc (both 9.1 and 10.1)
> - Redhat 4.4
> - Nodes are quad-core.  The mpd process is launched only
> once per node, but jobs are started using 4 cpus per node.
>
> Craig
>
> Craig Tierney wrote:
>>
>> I am trying to benchmark some applications on my system
>> and I have found something I did not expect with regards
>> to launch time of applications.
>>
>> All jobs are launched through a batch system (Sun Gridengine).
>> SGE is configured without tight-integration.  Since mpd has
>> to be setup for each user in each job, I have a wrapper script
>> that does roughly the following:
>>
>> -----------------------
>> $me=`uname -n`
>> $port=`mpd --ncpus=4 --echo --daemon --ifhn=$me-ib0`
>>
>> for every other node
>>    ssh $node mpd --ncpus=4 -h $me -p $port --daemon --ifhn=$node-ib0 &
>> end
>> waitall
>>
>> mpiexec -machinefile $machine_file $EXE
>> -----------------------
>>
>> I am running an MPI program that does very little.
>> It calls mpi_init, writes the hostname, then calls mpi_finalize.
>>
>> I measured the time it takes to launch mpd, the time it
>> takes for the program to execute (after MPI_init to just before
>> MPI_Finalize), and the time to call MPI_Init.
>>
>> Cores  mpd   complete  runjob
>> ------------------------------
>> 4     ~0.0    ~0.0      0.6
>> 16     0.6    ~0.0      0.8
>> 64     0.7    ~0.0      3.5
>> 128    1.0     0.2     11.2
>> 256    1.7     0.6     47.0
>> 324    2.1     0.1     76.4
>> 512    3.1     0.5    202.4
>>
>> - All timings are in seconds.
>>
>> mpd - the time to launch the mpd processes in parallel
>> complete - the time to run the application
>> runjob - the time to execute mpiexec
>>
>> My question is, why does mpd take so long to launch a job?
>> Am I doing something wrong?  Is there something I can do
>> to minimize the startup time?
>>
>> Thanks,
>> Craig
>>
>>
>>
>
>
> --
> Craig Tierney (craig.tierney at noaa.gov)
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