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Subject: Re: [OMPI users] very bad parallel scaling of vasp using openmpi
From: Patrick Geoffray (patrick_at_[hidden])
Date: 2009-08-18 15:54:32


Craig Plaisance wrote:
> So is this a problem with the physical switch (we need a better switch)
> or with the configuration of the switch (we need to configure the switch
> or configure the os to work with the switch)?

You may want to look if you are dropping packets somewhere. You can look
at the packet count on the sender and receiver interfaces and see if
they match (within epsilon). You can also look if your switch supports
hardware flow control, it would prevent packet loss is the receiver is
slower than the sender, but even slow/busy machines should be able to
receive 1 Gb/s these days.

What does ethtool -S ethX says on the worse sender/receiver pair ?

Patrick