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<font size=3>At 10:44 AM 6/9/2006, Scott Weitzenkamp (sweitzen)
wrote:<br>
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</font><font face="arial" size=2 color="#0000FF">While we're talking
about MTUs, is the IB MTU tunable in uDAPL and/or Intel MPI via env var
or config file?<br>
</font><font size=3> <br>
</font><font face="arial" size=2 color="#0000FF">Looks like Intel MPI
2.0.1 uses 2K for IB MTU like MVAPICH does in OFED 1.0 rc4 and rc6, I'd
like to try 1K with Intel MPI.</font></blockquote><font size=3><br>
IB MTU should be set on a per path basis by the SM. An application
should examine the PMTU for a given path and take appropriate action -
really only applies to UD as connected mode should automatically SAR
requests. Communicating PMTU to an application should not occur
unless it is datagram based. The same is true for iWARP where
TCP / IP takes care of the PMTU on behalf of the ULP / application.
If you want to control PMTU, then do so via the SM directly which was the
intention of the architecture and specification.<br><br>
Mike<br><br>
<blockquote type=cite class=cite cite=""> <br>
</font><font face="arial" size=2 color="#0000FF">Scott<br>
</font><font size=3><hr>
</font>
<dl>
<dd><font face="tahoma" size=2>From: openib-general-bounces@openib.org
[<a href="mailto:openib-general-bounces@openib.org" eudora="autourl">
mailto:openib-general-bounces@openib.org</a>] On Behalf Of Scott
Weitzenkamp (sweitzen)
<dd>Sent: Thursday, June 08, 2006 4:38 PM
<dd>To: Tziporet Koren; openfabrics-ewg@openib.org
<dd>Cc: openib-general
<dd>Subject: RE: [openib-general] OFED-1.0-rc6 is
available</font><font size=3></font>
<dd><font face="arial" size=2 color="#0000FF">The MTU change undos the
changes for bug 81, so I have reopened bug 81
(<a href="http://openib.org/bugzilla/show_bug.cgi?id=81">
http://openib.org/bugzilla/show_bug.cgi?id=81</a>).</font>
<dd><font size=3> </font>
<dd><font face="arial" size=2 color="#0000FF">With rc6, PCI-X osu_bw and
osu_bibw performance is bad, and PCI-E osu_bibw performance is bad.
I've enclosed some performance data, look at rc4 vs rc5 vs rc6 for
Cougar/Cheetah/LionMini.</font>
<dd><font size=3> </font>
<dd><font face="arial" size=2 color="#0000FF">Are there other benchmarks
driving the changes in rc6 (and rc4)?</font>
<dd><font size=3> </font>
<dd><font face="arial" size=2 color="#0000FF">Scott Weitzenkamp
<dd>SQA and Release Manager
<dd>Server Virtualization Business Unit
<dd>Cisco Systems</font>
<dd><font size=3> <br><br>
<dl>
<dd> <br><br>
</font>
<dd><font face="arial" size=2>OSU MPI:</font><font size=3></font>
<dd><font face="symbol" size=3>·</font>
<font face="Times New Roman, Times" size=1>
</font><font face="arial" size=2>Added mpi_alltoall fine tuning
parameters</font><font size=3></font>
<dd><font face="symbol" size=3>·</font>
<font face="Times New Roman, Times" size=1>
</font><font face="arial" size=2>Added default
configuration/documentation file
$MPIHOME/etc/mvapich.conf</font><font size=3></font>
<dd><font face="symbol" size=3>·</font>
<font face="Times New Roman, Times" size=1>
</font><font face="arial" size=2>Added shell configuration files
$MPIHOME/etc/mvapich.csh ,
$MPIHOME/etc/mvapich.csh</font><font size=3></font>
<dd><font face="symbol" size=3>·</font>
<font face="Times New Roman, Times" size=1>
</font><font face="arial" size=2>Default MTU was changed back to 2K for
InfiniHost III Ex and InfiniHost III Lx HCAs. For InfiniHost card
recommended value is:
<dd>VIADEV_DEFAULT_MTU=MTU1024</font><font size=3>
</dl>
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