PSM2 is the only valid implementation for OmniPath (OPA).  UCX also
supports OmniPath, but it does so via Verbs, thus getting much lower
performance (typically 3 GiB/s instead of 10 GiB/s).

To work around that, give the mtl_psm2 component a higher priority
than the pml_ucx component.

See <https://www.mail-archive.com/users@lists.open-mpi.org/msg33581.html>.

--- openmpi-4.0.2/ompi/mca/mtl/psm2/mtl_psm2_component.c	2019-11-15 17:06:15.142076840 +0100
+++ openmpi-4.0.2/ompi/mca/mtl/psm2/mtl_psm2_component.c	2019-11-15 17:06:22.242009379 +0100
@@ -126,7 +126,7 @@ ompi_mtl_psm2_component_register(void)
         setenv("PSM2_DEVICES", "self,shm", 0);
     }
 
-    param_priority = 40;
+    param_priority = 55;
     (void) mca_base_component_var_register (&mca_mtl_psm2_component.super.mtl_version,
                                             "priority", "Priority of the PSM2 MTL component",
                                             MCA_BASE_VAR_TYPE_INT, NULL, 0, 0,

Likewise for PSM: we want InfiniPath to be taken care of by PSM, not by UCX,
since UCX achieves worse performance.

--- openmpi-4.0.2/ompi/mca/mtl/psm/mtl_psm_component.c
+++ openmpi-4.0.2/ompi/mca/mtl/psm/mtl_psm_component.c
@@ -92,7 +92,7 @@ ompi_mtl_psm_component_register(void)
 
 
     /* set priority high enough to beat ob1's default */
-    param_priority = 30;
+    param_priority = 54;
     (void) mca_base_component_var_register (&mca_mtl_psm_component.super.mtl_version,
                                             "priority", "Priority of the PSM MTL component",
                                             MCA_BASE_VAR_TYPE_INT, NULL, 0, 0,
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<div class='path'>path: <a href='/guix/log/?id=77a1efed9e12ce0e2c470d7b0601ae70c72b010b'>root</a>/<a href='/guix/log/etc?id=77a1efed9e12ce0e2c470d7b0601ae70c72b010b'>etc</a>/<a href='/guix/log/etc/historical-authorizations?id=77a1efed9e12ce0e2c470d7b0601ae70c72b010b'>historical-authorizations</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/historical-authorizations?id=77a1efed9e12ce0e2c470d7b0601ae70c72b010b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-11 11:51:56 +0200'>2020-07-11</span></td><td><a href='/guix/commit/etc/historical-authorizations?id=4b9b8b2ec23e59af2275a6d2829e6e0f915b44b3'>Add 'etc/historical-authorizations'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>