diff --git a/src/framework/core/js/DataBinding.js b/src/framework/core/js/DataBinding.js
index b296633e21..81d5029d33 100644
--- a/src/framework/core/js/DataBinding.js
+++ b/src/framework/core/js/DataBinding.js
@@ -840,6 +840,8 @@ fluid.relayRecursionBailout = 100;
 // is transactional but it does not require the transaction to conclude in order to fire - it may be reused as many times as
 // required within the "overall" transaction whilst genuine (external) changes continue to arrive.
 
+fluid.count = 0;
+
 // TODO: Vast overcomplication and generation of closure garbage. SURELY we should be able to convert this into an externalised, arg-ist form
 /** Registers a listener operating one leg of a model relay relation, connecting the source and target. Called once or twice from `fluid.connectModelRelay` -
  * see the comment there for the three cases involved. Note that in its case iii)B) the applier to bind to is not the one attached to `target` but is instead
@@ -882,6 +884,9 @@ fluid.registerDirectChangeRelay = function (target, targetSegs, source, sourceSe
         }
         var transEl = transRec[applierId];
         transRec[linkId] = transRec[linkId] || 0;
+        ++fluid.count;
+        //fluid.log("SourceListener " + fluid.count + " firing with value " + JSON.stringify(newValue, null, 2) +  " from source ", source, " to target ", target,
+        //     " sourceSegs ", sourceSegs, " targetSegs ", targetSegs);
         // Crude "oscillation prevention" system limits each link to maximum of 2 operations per cycle (presumably in opposite directions)
         var relay = true; // TODO: See FLUID-5303 - we currently disable this check entirely to solve FLUID-5293 - perhaps we might remove link counts entirely
         if (relay) {
diff --git a/tests/framework-tests/core/js/DataBindingTests.js b/tests/framework-tests/core/js/DataBindingTests.js
index fac1966b02..0d16f54d72 100644
--- a/tests/framework-tests/core/js/DataBindingTests.js
+++ b/tests/framework-tests/core/js/DataBindingTests.js
@@ -1441,6 +1441,89 @@ jqUnit.test("FLUID-6390 V: Updating lensed components as an array", function ()
     fluid.tests.fluid6390assertModelValues("Updated model values are correct", that, []);
 });
 
+/** FLUID-6395 - Performance in fan-out of relays **/
+
+fluid.tests.fluid6395generate = function (fanOut) {
+    return fluid.generate(fanOut, function (index) {
+        return {
+            value: index
+        };
+    }, true);
+};
+
+fluid.defaults("fluid.tests.fluid6395root", {
+    gradeNames: "fluid.modelComponent",
+    fanOut: 200,
+    model: {
+        modelSource: "@expand:fluid.tests.fluid6395generate({that}.options.fanOut)"
+    },
+    dynamicComponents: {
+        child: {
+            sources: "{that}.model.modelSource",
+            type: "fluid.modelComponent",
+            options: {
+                model: {
+                    value: "{source}.value"
+                }
+            }
+        }
+    }
+});
+
+jqUnit.test("FLUID-6395: Performance of relay rules with increasing fan-out - fine-grained sharing", function () {
+    var that = fluid.tests.fluid6395root();
+    var children = fluid.queryIoCSelector(that, "fluid.modelComponent");
+    jqUnit.assertEquals("Constructed " + that.options.fanOut + " children: ", that.options.fanOut, children.length);
+    var now = Date.now();
+    children[0].applier.change("value", 999);
+    var elapsed = Date.now() - now;
+    jqUnit.assertEquals("Change relayed to parent model ", 999, that.model.modelSource[0].value);
+    fluid.log("Applied change in " + elapsed + "ms");
+});
+
+fluid.defaults("fluid.tests.fluid6395root2", {
+    gradeNames: "fluid.modelComponent",
+    fanOut: 100,
+    source: "@expand:fluid.tests.fluid6395generate({that}.options.fanOut)",
+    model: {
+        focus: {row: 0, col: 0}
+    },
+    components: {
+        midChild: {
+            type: "fluid.modelComponent",
+            options: {
+                model: {
+                    focus: "{fluid6395root2}.model.focus"
+                }
+            }
+        }
+    },
+    dynamicComponents: {
+        child: {
+            sources: "{that}.options.source",
+            type: "fluid.modelComponent",
+            options: {
+                model: {
+                    focus: "{midChild}.model.focus"
+                }
+            }
+        }
+    }
+});
+
+jqUnit.test("FLUID-6395 II: Performance of relay rules with increasing fan-out - coarse-grained sharing", function () {
+    var that = fluid.tests.fluid6395root2();
+    var children = fluid.queryIoCSelector(that, "fluid.modelComponent");
+    jqUnit.assertEquals("Constructed " + that.options.fanOut + " children: ", that.options.fanOut + 1, children.length);
+    var now = Date.now();
+    children[1].applier.change("focus", {row: 7, col: 5});
+    fluid.count = 0;
+    // that.applier.change("someValue", 999);
+    var elapsed = Date.now() - now;
+    jqUnit.assertEquals("Change relayed to parent model ", 7, that.model.focus.row);
+    fluid.log("Applied change in " + elapsed + "ms");
+});
+
 /** FLUID-6570: Short-form free transforms **/
 
 fluid.defaults("fluid.tests.fluid6570root", {