None

25 Jun 2026

      as less latency than 4KB.

I was looking for explanation of this behavior  but did not get any.

  1.  MPIR_CVAR_CH3_EAGER_MAX_MSG_SIZE is set to 128KB. So none of the abov=
e message size is using Rendezvous protocol. Is there any partition inside =
eager protocol (e.g. 0 - 512 bytes, 1KB - 8KB, 16KB - 64KB)? If yes then wh=
at are the boundaries for them? Can I log them with debug-event-logging?

Setup I am using: 

- two nodes has intel core i7, one with 16gb memory another one 8gb

- mpich 3.2.1, configured and build to use nemesis tcp

- 1gb Ethernet connection

- NFS is using for sharing

- osu_latency: uses MPI_Send and MPI_Recv

- MPIR_CVAR_CH3_EAGER_MAX_MSG_SIZE=3D 131072 (128KB)

Can anyone help me on that? Thanks in advance.

Best Regards,

Abu Naser

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<html><head>
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-=
1">
<style type=3D"text/css" style=3D"display: none;"><!-- P {margin-top:0;margi=
n-bottom: 0;} --></style>
</head>
<body dir=3D"ltr">
<div id=3D"divtagdefaultwrapper" dir=3D"ltr" style=3D"font-size: 12pt; color=
: rgb(0,0,0); font-family:Calibri,Helvetica,sans-serif,"EmojiFont"=
,"Apple Color Emoji","Segoe UI Emoji",NotoColorEmoji,&q=
uot;Segoe UI Symbol","Android Emoji",EmojiSymbols">
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">Good day to all,</p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">I had run point to point osu_lat=
ency test in two nodes for 200 times.  Followings are the average time=
 in microsecond for various size of the messages -</p>
<p style=3D"margin-top: 0; margin-bottom:0"></p>
<div>1KB    84.8514 us<br>
<span style=3D"color: rgb(255,0,0)">2KB    73.52535</span> us=
<br>
4KB    272.55275 us<br>
<span style=3D"color: rgb(255,0,0)">8KB    234.86385</span> u=
s<br>
16KB    288.88 us<br>
32KB    523.3725 us<br>
64KB    910.4025 us</div>
<p></p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">From the above looks like, 2KB m=
essage has less latency than 1 KB and 8KB has less latency than 4KB.
<br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">I was looking for explanation of=
 this behavior  but did not get any.</p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<ol style=3D"margin-bottom: 0px; margin-top:0px">
<li><span>MPIR_CVAR_CH3_EAGER_MAX_MSG_SIZE</span><span> is set to 128KB. So=
 none of the above message size is using Rendezvous protocol. Is there any =
partition inside eager protocol (e.g. 0 - 512 bytes, 1KB - 8KB, 16KB - 64KB=
)? If yes then what are the boundaries
 for them? Can I log them with debug-event-logging? </span><br>
</li></ol>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">Setup I am using:</p>
<p style=3D"margin-top: 0; margin-bottom:0">- two nodes has intel core i7, o=
ne with 16gb memory another one 8gb</p>
<p style=3D"margin-top: 0; margin-bottom:0">- mpich 3.2.1, configured and bu=
ild to use nemesis tcp</p>
<p style=3D"margin-top: 0; margin-bottom:0">- 1gb Ethernet connection</p>
<p style=3D"margin-top: 0; margin-bottom:0">- NFS is using for sharing<br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">- osu_latency : uses MPI_Send an=
d MPI_Recv</p>
<p style=3D"margin-top: 0; margin-bottom:0">- <span>MPIR_CVAR_CH3_EAGER_MAX_=
MSG_SIZE</span>=3D
<span>131072</span> (128KB)<br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0">Can anyone help me on that? Than=
ks in advance.<br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<p style=3D"margin-top: 0; margin-bottom:0"><br>
</p>
<div id=3D"Signature">
<div id=3D"divtagdefaultwrapper" dir=3D"ltr" style=3D"font-size: 12pt; color=
: rgb(0,0,0); font-family:Calibri,Helvetica,sans-serif,"EmojiFont"=
,"Apple Color Emoji","Segoe UI Emoji",NotoColorEmoji,&q=
uot;Segoe UI Symbol","Android Emoji",EmojiSymbols">
<p><br>
</p>
<p align=3D"left"><span style=3D"font-size: 10pt; font-family:Calibri,Helvet=
ica,sans-serif">Best Regards,</span></p>
<span style=3D"font-family: Calibri,Helvetica,sans-serif; font-size:10pt"></=
span>
<div align=3D"left"><span style=3D"font-size: 11pt; font-family:Calibri,Helv=
etica,sans-serif"></span></div>
<span style=3D"font-family: Calibri,Helvetica,sans-serif; font-size:10pt"></=
span>
<p align=3D"left"><span style=3D"font-size: 10pt; font-family:Calibri,Helvet=
ica,sans-serif">Abu Naser</span><br>
</p>
</div>
</div>
</div>
</body>
</html>

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