Hi Christian, list
I haven't been following the shared memory details of OMPI lately,
but my recollection from some time ago is that in the 1.8 series the
default (and recommended) shared memory transport btl switched from
"sm" to "vader", which is the latest greatest.
In this case, I guess the mpirun options would be:
mpirun --machinefile machine_mpi_bug.txt --mca btl self,vader,tcp
I am not even sure if with "vader" the "self" btl is needed,
as it was the case with "sm".
An OMPI developer could jump into this conversation and clarify.
Thank you.
I hope this helps,
Gus Correa
On 07/22/2015 04:42 AM, Crisitan RUIZ wrote:
Thank you for your answer Harald
Actually I was already using TAU before but it seems that it is not
maintained any more and there are problems when instrumenting
applications with the version 1.8.5 of OpenMPI.
I was using the OpenMPI 1.6.5 before to test the execution of HPC
application on Linux containers. I tested the performance of NAS
benchmarks in three different configurations:
- 8 Linux containers on the same machine configured with 2 cores
- 8 physical machines
- 1 physical machine
So, as I already described it, each machine counts with 2 processors (8
cores each). I instrumented and run all NAS benchmark in these three
configurations and I got the results that I attached in this email.
In the table "native" corresponds to using 8 physical machines and "SM"
corresponds to 1 physical machine using the sm module, time is given in
miliseconds.
What surprise me in the results is that using containers in the worse
case have equal communication time than just using plain mpi processes.
Even though the containers use virtual network interfaces to communicate
between them. Probably this behaviour is due to process binding and
locality, I wanted to redo the test using OpenMPI version 1.8.5 but
unfourtunately I couldn't sucessfully instrument the applications. I was
looking for another MPI profiler but I couldn't find any. HPCToolkit
looks like it is not maintain anymore, Vampir does not maintain any more
the tool that instrument the application. I will probably give a try to
Paraver.
Best regards,
Cristian Ruiz
On 07/22/2015 09:44 AM, Harald Servat wrote:
Cristian,
you might observe super-speedup heres because in 8 nodes you have 8
times the cache you have in only 1 node. You can also validate that by
checking for cache miss activity using the tools that I mentioned in
my other email.
Best regards.
On 22/07/15 09:42, Crisitan RUIZ wrote:
Sorry, I've just discovered that I was using the wrong command to run on
8 machines. I have to get rid of the "-np 8"
So, I corrected the command and I used:
mpirun --machinefile machine_mpi_bug.txt --mca btl self,sm,tcp
--allow-run-as-root mg.C.8
And got these results
8 cores:
Mop/s total = 19368.43
8 machines
Mop/s total = 96094.35
Why is the performance of mult-node almost 4 times better than
multi-core? Is this normal behavior?
On 07/22/2015 09:19 AM, Crisitan RUIZ wrote:
Hello,
I'm running OpenMPI 1.8.5 on a cluster with the following
characteristics:
Each node is equipped with two Intel Xeon E5-2630v3 processors (with 8
cores each), 128 GB of RAM and a 10 Gigabit Ethernet adapter.
When I run the NAS benchmarks using 8 cores in the same machine, I'm
getting almost the same performance as using 8 machines running a mpi
process per machine.
I used the following commands:
for running multi-node:
mpirun -np 8 --machinefile machine_file.txt --mca btl self,sm,tcp
--allow-run-as-root mg.C.8
for running in with 8 cores:
mpirun -np 8 --mca btl self,sm,tcp --allow-run-as-root mg.C.8
I got the following results:
8 cores:
Mop/s total = 19368.43
8 machines:
Mop/s total = 19326.60
The results are similar for other benchmarks. Is this behavior normal?
I was expecting to see a better behavior using 8 cores given that they
use directly the memory to communicate.
Thank you,
Cristian
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