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=d9d83b482c40c8fbeaa5074083b8f6042a83f2fa'>root</a>/<a href='/guix/log/nix?id=d9d83b482c40c8fbeaa5074083b8f6042a83f2fa'>nix</a>/<a href='/guix/log/nix/libstore?id=d9d83b482c40c8fbeaa5074083b8f6042a83f2fa'>libstore</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/nix/libstore?id=d9d83b482c40c8fbeaa5074083b8f6042a83f2fa&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-04-09 17:46:38 +0200'>2021-04-09</span></td><td><a href='/guix/commit/nix/libstore?id=2d73086262e1fb33cd0f0f16f74a495fe06b38aa'>daemon: 'guix substitute' replies on FD 4.</a><span class='msg-avail'>...<span class='msg-tooltip'>This avoids the situation where error messages would unintentionally go
to stderr and be wrongfully interpreted as a reply by the daemon.

Fixes &lt;https://bugs.gnu.org/46362&gt;.
This is a followup to ee3226e9d54891c7e696912245e4904435be191c.

* guix/scripts/substitute.scm (display-narinfo-data): Add 'port'
parameter and honor it.
(process-query): Likewise.
(process-substitution): Likewise.
(%error-to-file-descriptor-4?, with-redirected-error-port): Remove.
(%reply-file-descriptor): New variable.
(guix-substitute): Remove use of 'with-redirected-error-port'.  Define
'reply-port' and pass it to 'process-query' and 'process-substitution'.
* nix/libstore/build.cc (SubstitutionGoal::handleChildOutput): Swap
'builderOut' and 'fromAgent'.
* nix/libstore/local-store.cc (LocalStore::getLineFromSubstituter):
Likewise.
* tests/substitute.scm &lt;top level&gt;: Set '%reply-file-descriptor'
rather than '%error-to-file-descriptor-4?'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-03-18 12:18:56 +0100'>2021-03-18</span></td><td><a href='/guix/commit/nix/libstore?id=ec7fb669945bfb47c5e1fdf7de3a5d07f7002ccf'>daemon: Prevent privilege escalation with '--keep-failed' [security].</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/47229&gt;.
Reported by Nathan Nye of WhiteBeam Security.

* nix/libstore/build.cc (DerivationGoal::startBuilder): When 'useChroot'
is true, add "/top" to 'tmpDir'.
(DerivationGoal::deleteTmpDir): Adjust accordingly.  When
'settings.keepFailed' is true, chown in two steps: first the "/top"
sub-directory, and then rename "/top" to its parent.
</span></span></td><td>Ludovic Courtès</td></tr>