[Darshan-users] Darshan & EPCC benchio different behaviour

[Harms, Kevin]

Piero,

  the performance estimate is based on heuristics, it's possible the 'serial' model is breaking some assumptions about how the I/O is done. Is every rank opening the file, but only rank 0 is doing actual I/O?

  If possible, you could provide the log and we could check to see what the counters look like.

kevin

________________________________________
From: Piero LANUCARA <p.lanucara at cineca.it>
Sent: Tuesday, February 11, 2020 2:28 AM
To: Harms, Kevin
Cc: darshan-users at lists.mcs.anl.gov
Subject: Re: [Darshan-users] Darshan & EPCC benchio different behaviour

Hi Kevin

first of all thanks for the investigation..I did some futher test and it
seems like the issue may appear using Fortran (MPI, mainly IntelMPI) codes.

Is this information useful?

regards
Piero
Il 07/02/2020 16:07, Harms, Kevin ha scritto:
> Piero,
>
>    just to confirm, the serial case is still running in parallel, 36 processes, but the I/O is only from rank 0?
>
> kevin
>
> ________________________________________
> From: Darshan-users <darshan-users-bounces at lists.mcs.anl.gov> on behalf of Piero LANUCARA <p.lanucara at cineca.it>
> Sent: Wednesday, February 5, 2020 4:56 AM
> To: darshan-users at lists.mcs.anl.gov
> Subject: Re: [Darshan-users] Darshan & EPCC benchio different behaviour
>
> p.s
>
> to be more "verbose" I add to the discussion:
>
> Darshan output for the "serial" run (serial.pdf)
>
> Darshan output for the MPI-IO run (mpiio.pdf)
>
> benchio output for "serial" run (serial.out)
>
> benchio output for "MPI-IO" run (mpi-io.out)
>
> thanks
>
> Piero
>
> Il 04/02/2020 19:44, Piero LANUCARA ha scritto:
>> Dear all
>>
>> I'm using Darshan to measure EPCC benchio benchmark
>> (https://github.com/EPCCed/benchio) behaviour on a given x86 Tier1
>> machine.
>>
>> running two benchio tests (MPI-IO and serial) a different behaviour
>> appear
>>
>> while Darhsan pdf log file is able to recover the estimated time and
>> bandwidth in the MPI-IO case, the "serial" run is completely
>> underestimated by Darshan (the time and bandwidth are less/greater
>> than benchio output).
>>
>> Suggestions are welcomed
>>
>> thanks
>>
>> Piero
>>
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