UCX: Always use 2 RMA rails

There is no need to use four rails with IB, as it can cause performance
degradation in certain cases. This change was originally introduced for
AWS/EFA support, but the preferred plugin for EFA is now libfabric.

Signed-off-by: Mikhail Brinskii <[email protected]>

Author: brminich

src/utils/ucx/ucx_utils.cpp

@@ -452,18 +452,13 @@ nixlUcxContext::nixlUcxContext(std::vector<std::string> devs,
 
     config.modify ("ADDRESS_VERSION", "v2");
     config.modify ("RNDV_THRESH", "inf");
+    config.modify ("MAX_RMA_RAILS", "2");
 
     unsigned ucp_version = UCP_VERSION(major_version, minor_version);
     if (ucp_version >= UCP_VERSION(1, 19)) {
         config.modify ("MAX_COMPONENT_MDS", "32");
     }
 
-    if (ucp_version >= UCP_VERSION(1, 20)) {
-        config.modify ("MAX_RMA_RAILS", "4");
-    } else {
-        config.modify ("MAX_RMA_RAILS", "2");
-    }
-
     const auto status = ucp_init (&ucp_params, config.getUcpConfig(), &ctx);
     if (status != UCS_OK) {
         throw std::runtime_error ("Failed to create UCX context: " +