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Subject: Re: [OMPI users] Question on staging in checkpoint
From: Joshua Hursey (jjhursey_at_[hidden])
Date: 2010-09-13 17:44:19


Adjust the 'filem_rsh_max_incomming' parameter:
 http://osl.iu.edu/research/ft/ompi-cr/api.php#mca-filem_rsh_max_incomming

I defaulted this MCA parameter to 10 since, depending on how big each individual checkpoint is, you will find that often sending them all at once is often worse than sending only a window of them at a time. I would recommend trying a few different values for this parameter and seeing the impact it has both on checkpoint overhead (additional application overhead) and checkpoint latency (the time it takes for the checkpoint to completely finish).

-- Josh

On Sep 13, 2010, at 7:42 PM, <ananda.mudar_at_[hidden]> <ananda.mudar_at_[hidden]> wrote:

> Hi
>
> I was trying out the staging option in checkpoint where I save the checkpoint image in local file system and have the image transferred to global filesystem in the background. As part of the background process I see that the “scp” command is launched to transfer the images from local file system to global file system. I am using openmpi-1.5rc6 with BLCR 0.8.2.
>
> In my experiment, I had about 128 cores saved their respective checkpoint images on local file system. During the background process, I see that only 10 “scp” requests are sent at a time. Is this a configurable parameter? Since these commands will run on respective nodes, how can I launch all 128 scp requests (to take care of all 128 images in my experiment) simultaneously?
>
> Thanks
> Ananda
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------------------------------------
Joshua Hursey
Postdoctoral Research Associate
Oak Ridge National Laboratory
http://www.cs.indiana.edu/~jjhursey