Merge branch 'docs/admin_area_monitoring' into 'master'

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/57874

Closes #57874

See merge request gitlab-org/gitlab-ce!30013

doc/user/admin_area/index.md

@@ -21,7 +21,7 @@ The Admin Area is made up of the following sections:
 | Section                       | Description                                                                                                                                                                                                                                                                              |
 |:------------------------------|:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | [Overview](#overview-section) | View your GitLab [Dashboard](#admin-dashboard), and administer [projects](#administering-projects), [users](#administering-users), [groups](#administering-groups), [jobs](#administering-jobs), [Runners](#administering-runners), and [Gitaly servers](#administering-gitaly-servers). |
-| Monitoring                    | View GitLab system information, and information on background jobs, logs, [health checks](monitoring/health_check.md), request profiles, and audit logs.                                                                                                                                 |
+| Monitoring                    | View GitLab [system information](#system-info), and information on [background jobs](#background-jobs), [logs](#logs), [health checks](monitoring/health_check.md), [requests profiles](#requests-profiles), and [audit logs](#audit-log-premium-only).                                                                                                                                 |
 | Messages                      | Send and manage [broadcast messages](broadcast_messages.md) for your users.                                                                                                                                                                                                              |
 | System Hooks                  | Configure [system hooks](../../system_hooks/system_hooks.md) for many events.                                                                                                                                                                                                            |
 | Applications                  | Create system [OAuth applications](../../integration/oauth_provider.md) for integrations with other services.                                                                                                                                                                            |
@@ -229,3 +229,66 @@ For each Gitaly server, the following details are listed:
 | Server version | Gitaly version |
 | Git version    | Version of Git installed on the Gitaly server |
 | Up to date     | Indicates if the Gitaly server version is the latest version available. A green dot indicates the server is up to date. |
+
+## Monitoring section
+
+The following topics document the **Monitoring** section of the Admin Area.
+
+### System Info
+
+The **System Info** page provides the following statistics:
+
+| Field        | Description |
+| :----------- | :---------- |
+| CPU          | Number of CPU cores available |
+| Memory Usage | Memory in use, and total memory available |
+| Disk Usage   | Disk space in use, and total disk space available |
+| Uptime       | Approximate uptime of the GitLab instance |
+
+These statistics are updated only when you navigate to the **System Info** page, or you refresh the page in your browser.
+
+### Background Jobs
+
+The **Background Jobs** page displays the Sidekiq dashboard. Sidekiq is used by GitLab to
+perform processing in the background.
+
+The Sidekiq dashboard consists of the following elements:
+
+- A tab per jobs' status.
+- A breakdown of background job statistics.
+- A live graph of **Processed** and **Failed** jobs, with a selectable polling interval.
+- An historical graph of **Processed** and **Failed** jobs, with a selectable time span.
+- Redis statistics, including:
+  - Version number
+  - Uptime, measured in days
+  - Number of connections
+  - Current memory usage, measured in MB
+  - Peak memory usage, measured in MB
+
+### Logs
+
+The **Logs** page provides access to the following log files:
+
+| Log file                | Contents |
+| :---------------------- | :------- |
+| `application.log`       | GitLab user activity |
+| `githost.log`           | Failed GitLab interaction with Git repositories |
+| `production.log`        | Requests received from Unicorn, and the actions taken to serve those requests |
+| `sidekiq.log`           | Background jobs |
+| `repocheck.log`         | Repository activity |
+| `integrations_json.log` | Activity between GitLab and integrated systems |
+| `kubernetes.log`        | Kubernetes activity |
+
+The contents of these log files can be useful when troubleshooting a problem. Access is available to GitLab admins, without requiring direct access to the log files.
+
+For details of these log files and their contents, see [Log system](../../administration/logs.md).
+
+The content of each log file is listed in chronological order. To minimize performance issues, a maximum 2000 lines of each log file are shown.
+
+### Requests Profiles
+
+The **Requests Profiles** page contains the token required for profiling. For more details, see [Request Profiling](../../administration/monitoring/performance/request_profiling.md).
+
+### Audit Log **[PREMIUM ONLY]**
+
+The **Audit Log** page lists changes made within the GitLab server. With this information you can control, analyze, and track every change.