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I think the question on the libfabric list was interpreted as asking if you can use an ibv_mr returned by ibv_reg_mr with multiple NICs rather than I think what you're asking which is "can I register this memory buffer to multiple RDMA</div>
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<div dir="ltr">I think the question on the libfabric list was interpreted as asking if you can use an ibv_mr returned by ibv_reg_mr with multiple NICs rather than I think what you're asking which is "can I register this memory buffer to multiple RDMA NICs". If I understand this correctly, in the latter case you would have multiple ibv_mr's (one per RDMA NIC) that all point to the same memory address and in the former case you would be attempting to use a single ibv_mr on multiple NICs.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Aug 21, 2024 at 12:21 PM Niyaz Murshed via Mvapich-discuss <<a href="mailto:mvapich-discuss@lists.osu.edu">mvapich-discuss@lists.osu.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg6259728952793989199">
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ibv_reg_mr takes in PD and buffer. Each PD is associated with a HCA. If we register the buffer with multiple PDs, it can be access by all HCAs? My understanding from another source is that “ibverbs” do not support this. ‘Some providers (e. g. </div>
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<p class="MsoNormal"><span style="font-size:11pt">ibv_reg_mr takes in PD and buffer. Each PD is associated with a HCA.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">If we register the buffer with multiple PDs, it can be access by all HCAs?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">My understanding from another source is that “ibverbs” do not support this.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">‘Some providers (e.g. verbs) map domain to a specific nic and thus can't share MR among nics.’<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><a href="https://urldefense.com/v3/__https://lists.openfabrics.org/pipermail/libfabric-users/2024-August/001072.html__;!!KGKeukY!zUrZMd5JRh1pubI8Fuu1XwdWwMy2uLWiA-K4phQvn8l2tX9sKky66SvWrNI6KNax2SuTyiVci0mUwI9et7neP0SHWlrREto$" target="_blank">https://lists.openfabrics.org/pipermail/libfabric-users/2024-August/001072.html</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
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<p class="MsoNormal" style="margin-bottom:12pt"><b><span style="font-size:12pt;color:black">From:
</span></b><span style="font-size:12pt;color:black">Subramoni, Hari <<a href="mailto:subramoni.1@osu.edu" target="_blank">subramoni.1@osu.edu</a>><br>
<b>Date: </b>Wednesday, August 21, 2024 at 11:15</span><span style="font-size:12pt;font-family:Arial,sans-serif;color:black"> </span><span style="font-size:12pt;color:black">AM<br>
<b>To: </b>Niyaz Murshed <<a href="mailto:Niyaz.Murshed@arm.com" target="_blank">Niyaz.Murshed@arm.com</a>>, Announcement about MVAPICH (MPI over InfiniBand, RoCE, Omni-Path, Slingshot, iWARP and EFA) Libraries developed at NBCL/OSU <<a href="mailto:mvapich-discuss@lists.osu.edu" target="_blank">mvapich-discuss@lists.osu.edu</a>><br>
<b>Cc: </b>nd <<a href="mailto:nd@arm.com" target="_blank">nd@arm.com</a>>, Subramoni, Hari <<a href="mailto:subramoni.1@osu.edu" target="_blank">subramoni.1@osu.edu</a>><br>
<b>Subject: </b>RE: RDMA memory registration for AllGather<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif">Hi, Niyaz.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif">One buffer can be registered with multiple HCAs. There is no problem with this. You just to call ibv_reg_mr multiple times.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif">Thx,</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif">Hari.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"> Mvapich-discuss <<a href="mailto:mvapich-discuss-bounces@lists.osu.edu" target="_blank">mvapich-discuss-bounces@lists.osu.edu</a>>
<b>On Behalf Of </b>Niyaz Murshed via Mvapich-discuss<br>
<b>Sent:</b> Tuesday, August 20, 2024 3:18 PM<br>
<b>To:</b> Niyaz Murshed via Mvapich-discuss <<a href="mailto:mvapich-discuss@lists.osu.edu" target="_blank">mvapich-discuss@lists.osu.edu</a>><br>
<b>Cc:</b> nd <<a href="mailto:nd@arm.com" target="_blank">nd@arm.com</a>><br>
<b>Subject:</b> [Mvapich-discuss] RDMA memory registration for AllGather</span><u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:1pt;color:white">Hello all , I am trying to understand how a single memory buffer is registered to multiple rdma verbvs context in case there are data coming in from different interfaces. As I understand, we can
only register RDMA memory to a single protection</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt">Hello all , </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">I am trying to understand how a single memory buffer is registered to multiple rdma verbvs context in case there are data coming in from different interfaces.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">As I understand, we can only register RDMA memory to a single protection domain which is linked to one interface.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">Assuming we receive data from 3 ranks on interface1 and 2 ranks from interface 2, how do these interfaces write to same common buffer ?</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">How is the same buffer registered to 2 interfaces?</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">Regards,</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt">Niyaz</span><u></u><u></u></p>
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