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Subject: Re: [OMPI users] IMB-MPI broadcast test stalls for large core counts: debug ideas?
From: Randolph Pullen (randolph_pullen_at_[hidden])
Date: 2010-08-24 21:54:20


Std TCP/IP stack
it hung with an unknown but large(ish) quantity of data.  when I ran just one Bcast it was fine but Bcasts in lots in separate MPI_WORLD's hung.   - All the details are in some recent posts.

I could not figure it out and moved back to my PVM solution.

--- On Wed, 25/8/10, Rahul Nabar <rpnabar_at_[hidden]> wrote:

From: Rahul Nabar <rpnabar_at_[hidden]>
Subject: Re: [OMPI users] IMB-MPI broadcast test stalls for large core counts: debug ideas?
To: "Open MPI Users" <users_at_[hidden]>
Received: Wednesday, 25 August, 2010, 3:38 AM

On Mon, Aug 23, 2010 at 8:39 PM, Randolph Pullen
<randolph_pullen_at_[hidden]> wrote:
>
> I have had a similar load related problem with Bcast.

Thanks Randolph! That's interesting to know! What was the hardware you
were using? Does your bcast fail at the exact same point too?

>
> I don't know what caused it though.  With this one, what about the possibility of a buffer overrun or network saturation?

How can I test for a buffer overrun?

For network saturation I guess I could use something like mrtg to
monitor the bandwidth used. On the other hand, all 32 servers are
connected to a single dedicated Nexus5000. The back-plane carries no
other traffic. Hence I am skeptical that just 41943040 saturated what
Cisco rates as a 10GigE fabric. But I might be wrong.

-- 
Rahul
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