Add prometheus memory requirements, include additional detail on disabling prometheus in docs.

doc/administration/monitoring/prometheus/index.md

@@ -22,26 +22,22 @@ dashboard tool like [Grafana].
 ## Configuring Prometheus
 
 >**Note:**
-Available since Omnibus GitLab 8.16. For installations from source you'll
-have to install and configure it yourself.
+- For installations from source you'll have to install and configure it yourself.
 
-To enable Prometheus:
+Prometheus and it's exporters are on by default, starting with GitLab 9.0. Prometheus will run as the `gitlab-prometheus` user and listen on `http://localhost:9090`. Each exporter will be automatically be set up as a monitoring target for Prometheus, unless individually disabled.
+
+To disable Prometheus and all of its exporters, as well as any added in the future:
 
 1. Edit `/etc/gitlab/gitlab.rb`
 1. Add or find and uncomment the following line, making sure it's set to `true`:
 
     ```ruby
-    prometheus['enable'] = true
+    prometheus['disable_all'] = true
     ```
 
 1. Save the file and [reconfigure GitLab][reconfigure] for the changes to
    take effect
 
-By default, Prometheus will run as the `gitlab-prometheus` user and listen on
-`http://localhost:9090`. If the [node exporter](#node-exporter) service
-has been enabled, it will automatically be set up as a monitoring target for
-Prometheus.
-
 ## Changing the port Prometheus listens on
 
 >**Note:**
@@ -67,8 +63,7 @@ To change the address/port that Prometheus listens on:
 
 ## Viewing performance metrics
 
-After you have [enabled Prometheus](#configuring-prometheus), you can visit
-`http://localhost:9090` for the dashboard that Prometheus offers by default.
+You can visit `http://localhost:9090` for the dashboard that Prometheus offers by default.
 
 >**Note:**
 If SSL has been enabled on your GitLab instance, you may not be able to access

doc/install/requirements.md

@@ -108,7 +108,7 @@ use the CI features.
 
 ## Unicorn Workers
 
-It's possible to increase the amount of unicorn workers and this will usually help for to reduce the response time of the applications and increase the ability to handle parallel requests.
+It's possible to increase the amount of unicorn workers and this will usually help to reduce the response time of the applications and increase the ability to handle parallel requests.
 
 For most instances we recommend using: CPU cores + 1 = unicorn workers.
 So for a machine with 2 cores, 3 unicorn workers is ideal.
@@ -148,6 +148,12 @@ Sidekiq processes the background jobs with a multithreaded process.
 This process starts with the entire Rails stack (200MB+) but it can grow over time due to memory leaks.
 On a very active server (10,000 active users) the Sidekiq process can use 1GB+ of memory.
 
+## Prometheus and its exporters
+
+As of GitLab 9.0, [Prometheus](https://prometheus.io) and its related exporters are enabled by default, to enable easy and in depth monitoring of GitLab. Approximately 200MB of memory will be consumed by these processes, with default settings.
+
+If you would like to disable Prometheus and it's exporters, simply set `prometheus['disable_all']=true` in `gitlab.rb`. More information is available in [the documentation](https://docs.gitlab.com/ce/doc/administration/monitoring/prometheus/index.html).
+
 ## Supported web browsers
 
 We support the current and the previous major release of Firefox, Chrome/Chromium, Safari and Microsoft browsers (Microsoft Edge and Internet Explorer 11).