Add documentation of daily pipelines per schedule limit

doc/administration/instance_limits.md

@@ -397,6 +397,31 @@ To set this limit for a self-managed installation, run the following in the
 Plan.default.actual_limits.update!(ci_pipeline_schedules: 100)
 ```
 
+### Limit the number of pipelines created by a pipeline schedule per day
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/323066) in GitLab 14.0.
+
+You can limit the number of pipelines that pipeline schedules can trigger per day.
+
+Schedules that try to run pipelines more frequently than the limit are slowed to a maximum frequency.
+The frequency is calculated by dividing 1440 (the number minutes in a day) by the
+limit value. For example, for a maximum frequency of:
+
+- Once per minute, the limit must be `1440`.
+- Once per 10 minutes, the limit must be `144`.
+- Once per 60 minutes, the limit must be `24`
+
+There is no limit for self-managed instances by default.
+
+To set this limit to `1440` on a self-managed installation, run the following in the
+[GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session):
+
+```ruby
+Plan.default.actual_limits.update!(ci_daily_pipeline_schedule_triggers: 1440)
+```
+
+This limit is [enabled on GitLab.com](../user/gitlab_com/index.md#gitlab-cicd).
+
 ### Number of instance level variables
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/216097) in GitLab 13.1.

doc/user/gitlab_com/index.md

@@ -136,6 +136,7 @@ the related documentation.
 | [Max jobs in active pipelines](../../administration/instance_limits.md#number-of-jobs-in-active-pipelines) | `500` for Free tier, unlimited otherwise | Unlimited |
 | [Max CI/CD subscriptions to a project](../../administration/instance_limits.md#number-of-cicd-subscriptions-to-a-project) | `2` | Unlimited |
 | [Max pipeline schedules in projects](../../administration/instance_limits.md#number-of-pipeline-schedules) | `10` for Free tier, `50` for all paid tiers | Unlimited |
+| [Max pipelines per schedule](../../administration/instance_limits.md#limit-the-number-of-pipelines-created-by-a-pipeline-schedule-per-day) | `24` for Free tier, `288` for all paid tiers | Unlimited |
 | [Scheduled Job Archival](../../user/admin_area/settings/continuous_integration.md#archive-jobs) | 3 months | Never |
 | Max test cases per [unit test report](../../ci/unit_test_reports.md) | `500_000` | Unlimited |
 | [Max registered runners](../../administration/instance_limits.md#number-of-registered-runners-per-scope) | `50` per-project and per-group for Free tier,<br/>`1_000` per-group for all paid tiers / `1_000` per-project for all paid tiers | `1_000` per-group / `1_000` per-project |