Re: [OMPI users] mpirun with -am ft-enable-cr option takes longer time on certain configurations

[Josh Hursey]

On Mar 20, 2010, at 11:14 PM,   wrote:


I am observing a very strange performance issue with my openmpi  
program.


I have compute intensive openmpi based application that keeps the  
data in memory, process the data and then dumps it to GPFS parallel  
file system. GPFS parallel file system server is connected to a QDR  
infiniband switch from Voltaire.


If my cluster is connected to a DDR infiniband switch which in turn  
connects to file system server on QDR switch, I see that I can run  
my application under checkpoint/restart control (with –am ft-enable- 
cr) and I can checkpoint (ompi-checkpoint) successfully and the  
application gets completed after few additional seconds.


If my cluster is connected to the same QDR switch which connects to  
file system server, I see that my application takes close to 10x  
time to complete if I run it under checkpoint/restart control (with – 
am ft-enable-cr). If I run the same application using a plain mpirun  
command (ie; without -am ft_enable_cr), it finishes within a minute.


The 10x slowdown is without taking a checkpoint, correct? If the  
checkpoint is taking up part of the bandwidth through the same switch  
you are communicating with, then you will see diminished performance  
until the checkpoint is fully established on the storage device(s).  
Many installations separate the communication and storage networks (or  
limiting the bandwidth of one of them) to prevent one from  
unexpectedly demising the performance of the other, even outside of  
the C/R context.


However for a non-checkpointing run to be 10x slower is certainly not  
normal. Try playing with the C/R thread parameters (mentioned in a  
previous email) and see if that helps. If not, we might be able to try  
other things.


-- Josh 





I am using open mpi 1.3.4 and BLCR 0.8.2 for checkpointing

Are there any specific MCA parameters that I should tune to address  
this problem? Any other pointers will be really helpful.


Thanks
Anand
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[OMPI users] mpirun with -am ft-enable-cr option takes longer time on certain configurations

[ananda.mudar]

I am observing a very strange performance issue with my openmpi program.



I have compute intensive openmpi based application that keeps the data
in memory, process the data and then dumps it to GPFS parallel file
system. GPFS parallel file system server is connected to a QDR
infiniband switch from Voltaire.



If my cluster is connected to a DDR infiniband switch which in turn
connects to file system server on QDR switch, I see that I can run my
application under checkpoint/restart control (with -am ft-enable-cr) and
I can checkpoint (ompi-checkpoint) successfully and the application gets
completed after few additional seconds.



If my cluster is connected to the same QDR switch which connects to file
system server, I see that my application takes close to 10x time to
complete if I run it under checkpoint/restart control (with -am
ft-enable-cr). If I run the same application using a plain mpirun
command (ie; without -am ft_enable_cr), it finishes within a minute.



I am using open mpi 1.3.4 and BLCR 0.8.2 for checkpointing



Are there any specific MCA parameters that I should tune to address this
problem? Any other pointers will be really helpful.



Thanks

Anand


Please do not print this email unless it is absolutely necessary. 

The information contained in this electronic message and any attachments to 
this message are intended for the exclusive use of the addressee(s) and may 
contain proprietary, confidential or privileged information. If you are not the 
intended recipient, you should not disseminate, distribute or copy this e-mail. 
Please notify the sender immediately and destroy all copies of this message and 
any attachments. 

WARNING: Computer viruses can be transmitted via email. The recipient should 
check this email and any attachments for the presence of viruses. The company 
accepts no liability for any damage caused by any virus transmitted by this 
email. 

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