[skip ci] Add go_memstats_frees_total metric to grafana (#7893)

Signed-off-by: Edward Zeng <jie.zeng@zilliz.com>

deployments/monitor/grafana/milvus-dashboard.json

@@ -16,7 +16,7 @@
   "gnetId": null,
   "graphTooltip": 0,
   "id": 25,
-  "iteration": 1631601711802,
+  "iteration": 1631607697292,
   "links": [],
   "panels": [
     {
@@ -5161,6 +5161,104 @@
         "align": false,
         "alignLevel": null
       }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "$datasource",
+      "description": "Rate of memory frees.",
+      "fieldConfig": {
+        "defaults": {},
+        "overrides": []
+      },
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 6,
+        "w": 8,
+        "x": 0,
+        "y": 27
+      },
+      "hiddenSeries": false,
+      "id": 123213,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "alertThreshold": true
+      },
+      "percentage": false,
+      "pluginVersion": "7.5.10",
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "exemplar": true,
+          "expr": "rate(go_memstats_frees_total{app_kubernetes_io_name=\"$app_name\", app_kubernetes_io_instance=~\"$instance\", namespace=\"$namespace\"}[5m])",
+          "interval": "",
+          "intervalFactor": 2,
+          "legendFormat": "{{component}}: {{pod}}",
+          "queryType": "randomWalk",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Memory Free Rate",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "decimals": null,
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": "0",
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
     }
   ],
   "refresh": false,
@@ -5343,5 +5441,5 @@
   "timezone": "browser",
   "title": "Milvus2.0",
   "uid": "uLf5cJ3Gz",
-  "version": 90
+  "version": 91
 }