Remove msg_store_credit_disc_bound

I'm fairly sure this setting doesn't change anything in practice and even if it does - I don't think anyone should be teaking it. We'll likely remove it altogether in the future. While at it, add a warning to an old blog post about credit flow.
rabbitmq · Jan 14, 2025 · 320071d · 320071d
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diff --git a/blog/2015-10-06-new-credit-flow-settings-on-rabbitmq-3-5-5/index.md b/blog/2015-10-06-new-credit-flow-settings-on-rabbitmq-3-5-5/index.md
@@ -4,6 +4,14 @@ tags: ["Performance", ]
 authors: [alvaro]
 ---
 
+:::warning
+This blog post was written for RabbitMQ 3.5, released in 2015. While some parts still
+apply, there's a lot of outdated information. For example, RabbitMQ 4.0
+doesn't support queue mirroring anymore and "paging messages to disk" is
+no longer something that RabbitMQ has to do, since messages are almost
+always persisted to disk right away.
+:::
+
 In order to prevent fast publishers from overflowing the broker with
 more messages than it can handle at any particular moment, RabbitMQ
 implements an internal mechanism called *credit flow* that will be

diff --git a/docs/configure.md b/docs/configure.md
@@ -1438,33 +1438,6 @@ under the `rabbit` section.
         </p>
       </td>
     </tr>
-  <tr>
-    <td>`msg_store_credit_disc_bound`</td>
-    <td>
-      The credits that a queue process is given by the message store.
-      <p>
-        By default, a queue process is given 4000 message store credits, and then 800 for every 800 messages that it processes.
-      </p>
-      <p>
-        Messages which need to be paged out due to memory pressure will also use this credit.
-      </p>
-      <p>
-        The Message Store is the last component in the credit flow chain. [Learn about credit flow](/blog/2015/10/06/new-credit-flow-settings-on-rabbitmq-3-5-5).
-      </p>
-      <p>
-        This value only takes effect when messages are persisted to the message store.
-        If messages are embedded on the queue index, then modifying this setting has no effect because credit_flow is NOT used when writing to the queue index.
-      </p>
-      <p>
-        Default:
-```erlang
-{rabbit, [
-{msg_store_credit_disc_bound, {4000, 800}}
-]}
-```
-      </p>
-    </td>
-  </tr>
   <tr>
     <td>`queue_index_max_journal_entries`</td>
     <td>

diff --git a/versioned_docs/version-4.0/configure.md b/versioned_docs/version-4.0/configure.md
@@ -1438,33 +1438,6 @@ under the `rabbit` section.
         </p>
       </td>
     </tr>
-  <tr>
-    <td>`msg_store_credit_disc_bound`</td>
-    <td>
-      The credits that a queue process is given by the message store.
-      <p>
-        By default, a queue process is given 4000 message store credits, and then 800 for every 800 messages that it processes.
-      </p>
-      <p>
-        Messages which need to be paged out due to memory pressure will also use this credit.
-      </p>
-      <p>
-        The Message Store is the last component in the credit flow chain. [Learn about credit flow](/blog/2015/10/06/new-credit-flow-settings-on-rabbitmq-3-5-5).
-      </p>
-      <p>
-        This value only takes effect when messages are persisted to the message store.
-        If messages are embedded on the queue index, then modifying this setting has no effect because credit_flow is NOT used when writing to the queue index.
-      </p>
-      <p>
-        Default:
-```erlang
-{rabbit, [
-{msg_store_credit_disc_bound, {4000, 800}}
-]}
-```
-      </p>
-    </td>
-  </tr>
   <tr>
     <td>`queue_index_max_journal_entries`</td>
     <td>