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<p class=MsoNormal><b><font size=2 color=black face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold'>From:</span></font></b><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'> openib-general-bounces@openib.org
[mailto:openib-general-bounces@openib.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>hbchen<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, June 05, 2006 9:12
AM<br>
<b><span style='font-weight:bold'>To:</span></b> Talpey, Thomas<br>
<b><span style='font-weight:bold'>Cc:</span></b> openib-general@openib.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [openib-general]
Question about the IPoIB bandwidth performance ?</span></font><font
color=black><span style='color:windowtext'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
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<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>Talpey, Thomas wrote:<br>
<br>
<o:p></o:p></span></font></p>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>At 11:38 AM 6/5/2006, hbchen wrote:<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite><pre wrap=""><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Even with this IB-4X = 8Gb/sec = 1024 MB/sec the IPoIB bandwidth utilization is still very low.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite><pre wrap=""><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>IPoIB=420MB/sec <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>bandwidth utilization= 420/1024 = 41.01%<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre></blockquote>
</blockquote>
</blockquote>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Helen, have you measured the CPU utilizations during these runs?<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Perhaps you are out of CPU.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>Tom,<br>
I am HB Chen from LANL not the Helen Chen from SNL.<br>
I didn't run out of CPU. It is about 70-80 % of CPU utilization.<br>
<br>
<br>
<o:p></o:p></span></font></p>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>Outrageous opinion follows.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Frankly, an IB HCA running Ethernet emulation is approximately the<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>world's worst 10GbE adapter (not to put too fine of a point on it :-) )<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>The IP over Myrinet ( Ethernet emulation) can reach
upto 96%-98% bandwidth utilization why not the IPoIB ?<br>
<br>
</span></font><font color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><b><i><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy;font-weight:bold;
font-style:italic'>[Felix:] As pointed out earlier: it is the message rate. If
you change the mtu to 1500B (instead of the non-standard 9000B Jumbo frames)
performance will drop into the same range as what you see with IPoIB (limited
by the receiver).<o:p></o:p></span></font></i></b></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><br>
HB Chen <br>
<a href="mailto:hbchen@lanl.gov">hbchen@lanl.gov</a><br>
<br>
<o:p></o:p></span></font></p>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>There is no hardware checksumming, nor large-send offloading, both<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>of which force overhead onto software. And, as you just discovered<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>it isn't even 10Gb!<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>In general, network emulation layers are always going to perform more<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>poorly than native implementations. But this is only a generality learned<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>from years of experience with them.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Tom. <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
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