cloud: update Request Units per Second metric for Premium (#22878)

Author: hfxsd

tidb-cloud/premium/built-in-monitoring-premium.md

@@ -31,7 +31,7 @@ The following sections illustrate the metrics on the **Metrics** page for {{{ .p
 
 | Metric name  | Labels | Description                                   |
 | :------------| :------| :-------------------------------------------- |
-| Request Units per Second | Total RU per second | The Request Unit (RU) is a unit of measurement used to track the resource consumption of a query or transaction. In addition to queries that you run, request units can be consumed by background activities, so when the QPS is 0, the request units per second might  not be zero. |
+| Request Units per Second | Total RU per second, AVG RU/s | The Request Unit (RU) is a unit of measurement used to track the resource consumption of a query or transaction. `Total RU per second` displays the real-time RU consumption per second. `AVG RU/s` displays the average RU consumption per second over the selected time range, helping you better understand resource consumption. In addition to queries that you run, background activities can also consume RUs. Therefore, when the QPS is 0, the RU consumption per second might still be greater than 0. |
 | Used Storage Size | {type} | The size of the row store and the size of the column store. |
 | Query Per Second | All, {SQL type} | The number of SQL statements executed per second, which are collected by SQL types, such as `SELECT`, `INSERT`, and `UPDATE`. |
 | Query Duration | avg, avg-{SQL type}, 99, 99-{SQL type} | The duration from receiving a request from the client to TiDB until TiDB executes the request and returns the result to the client. |

tidb-cloud/releases/tidb-cloud-release-notes.md

@@ -12,6 +12,12 @@ This page lists the release notes of [TiDB Cloud](https://www.pingcap.com/tidb-c
 
 **General changes**
 
+- **TiDB Cloud Premium**
+
+    - Add the `AVG RU/s` metric to the [TiDB Cloud Premium](https://docs.pingcap.com/tidbcloud/premium/?plan=premium) **Metrics** page.
+    
+        `AVG RU/s` displays the average number of RUs consumed per second over the selected time range, helping you better understand resource consumption.
+
 - **TiDB Cloud Dedicated**
 
     - [TiDB Cloud Dedicated](/tidb-cloud/select-cluster-tier.md#tidb-cloud-dedicated) is now generally available (GA) on Microsoft Azure in **Japan East** and **East US 2**.