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<p class="MsoNormal"><span style="font-size:11.0pt">In the most general case, a packet would take a round-trip travel on the wire: Tx engine
</span><span style="font-size:11.0pt;font-family:Wingdings">à</span><span style="font-size:11.0pt"> wire
</span><span style="font-size:11.0pt;font-family:Wingdings">à</span><span style="font-size:11.0pt"> switch or loopback cable
</span><span style="font-size:11.0pt;font-family:Wingdings">à</span><span style="font-size:11.0pt"> wire
</span><span style="font-size:11.0pt;font-family:Wingdings">à</span><span style="font-size:11.0pt"> Rx engine. However, most NICs have a loopback path between the TX and RX engines so that the packet doesn’t need to go out to the wire for local bound communication.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">-Jianxin <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Niyaz Murshed <Niyaz.Murshed@arm.com>
<br>
<b>Sent:</b> Friday, August 30, 2024 8:25 AM<br>
<b>To:</b> Xiong, Jianxin <jianxin.xiong@intel.com>; libfabric-users@lists.openfabrics.org<br>
<b>Cc:</b> nd <nd@arm.com><br>
<b>Subject:</b> Re: Multi process on same domain<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thank you Jianxin.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">yes, I meant 1 NIC being shared by 2 processes talking to each other on verbs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I was wondering how the data is being exchanged between the QPs created since both QPs are on the same NIC.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Another test I am planning to do is as below :<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">2 servers , with 1 NIC connected to each other.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Client on Server A writes to Server on B over the NIC<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Client on Server B writes to Server on A over the same NIC.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Basically, sharing the same NIC to send and receive work requests. These are just to understand the message flows in verbs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Xiong, Jianxin <</span><a href="mailto:jianxin.xiong@intel.com"><span style="font-size:12.0pt">jianxin.xiong@intel.com</span></a><span style="font-size:12.0pt;color:black">><br>
<b>Date: </b>Friday, August 30, 2024 at 10:17</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-size:12.0pt;color:black">AM<br>
<b>To: </b>Niyaz Murshed <</span><a href="mailto:Niyaz.Murshed@arm.com"><span style="font-size:12.0pt">Niyaz.Murshed@arm.com</span></a><span style="font-size:12.0pt;color:black">>,
</span><a href="mailto:libfabric-users@lists.openfabrics.org"><span style="font-size:12.0pt">libfabric-users@lists.openfabrics.org</span></a><span style="font-size:12.0pt;color:black"> <</span><a href="mailto:libfabric-users@lists.openfabrics.org"><span style="font-size:12.0pt">libfabric-users@lists.openfabrics.org</span></a><span style="font-size:12.0pt;color:black">><br>
<b>Cc: </b>nd <</span><a href="mailto:nd@arm.com"><span style="font-size:12.0pt">nd@arm.com</span></a><span style="font-size:12.0pt;color:black">><br>
<b>Subject: </b>RE: Multi process on same domain<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Libfabric “domain” is a per-process concept, so it is meaningless to talk about libfabric domain cross multiple processes.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The “-d” argument in the example specify the domain name, which maps to NIC device name for verbs. It is totally fine to create multiple domains with the same name.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">A Verbs port can always be shared by multiple processes. Each process has its own “user context” when the Verbs device/port is opened. Note that the verbs “port number” is part of the device identification.
It’s different from the port number used in TCP connections.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">-Jianxin <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Libfabric-users <</span><a href="mailto:libfabric-users-bounces@lists.openfabrics.org"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">libfabric-users-bounces@lists.openfabrics.org</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">>
<b>On Behalf Of </b>Niyaz Murshed<br>
<b>Sent:</b> Friday, August 30, 2024 7:27 AM<br>
<b>To:</b> </span><a href="mailto:libfabric-users@lists.openfabrics.org"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">libfabric-users@lists.openfabrics.org</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><br>
<b>Cc:</b> nd <</span><a href="mailto:nd@arm.com"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">nd@arm.com</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">><br>
<b>Subject:</b> [libfabric-users] Multi process on same domain</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Hello, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">How do messages pass from QP to QP when both server and client are using the same domain?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I can see RoCE packets in Wireshark, so it does go to the NIC.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Client :<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">fi_rma_bw -s 192.168.2.100 -e msg -I 1 -S 1024 -p verbs -w 0 -o writedata 192.168.2.100 -d mlx5_2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Server:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">fi_rma_bw -s 192.168.2.100 -e msg -I 1 -S 1024 -p verbs -w 0 -o writedata -d mlx5_2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I am trying to understand how multiple process/thread can share the same port over Verbs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Niyaz<o:p></o:p></span></p>
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