From 25f1916b6fb8321733982dafeeb047bc91e95f7c Mon Sep 17 00:00:00 2001
From: H-Shay <H-Shay@users.noreply.github.com>
Date: Fri, 13 May 2022 19:33:14 +0000
Subject: deploy: cde8af9a495cbc7f3d0207e3f17c37eddaee34e1

---
 .../usage/configuration/config_documentation.html    | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

(limited to 'develop/usage/configuration/config_documentation.html')

diff --git a/develop/usage/configuration/config_documentation.html b/develop/usage/configuration/config_documentation.html
index ab92ac22ce..10bcd93e9a 100644
--- a/develop/usage/configuration/config_documentation.html
+++ b/develop/usage/configuration/config_documentation.html
@@ -1049,14 +1049,32 @@ with intermittent connections, at the cost of higher memory usage.
 By default, this is zero, which means that sync responses are not cached
 at all.</p>
 </li>
+<li>
+<p><code>cache_autotuning</code> and its sub-options <code>max_cache_memory_usage</code>, <code>target_cache_memory_usage</code>, and
+<code>min_cache_ttl</code> work in conjunction with each other to maintain a balance between cache memory 
+usage and cache entry availability. You must be using <a href="https://github.com/matrix-org/synapse#help-synapse-is-slow-and-eats-all-my-ramcpu">jemalloc</a> 
+to utilize this option, and all three of the options must be specified for this feature to work.</p>
+<ul>
+<li><code>max_cache_memory_usage</code> sets a ceiling on how much memory the cache can use before caches begin to be continuously evicted.
+They will continue to be evicted until the memory usage drops below the <code>target_memory_usage</code>, set in
+the flag below, or until the <code>min_cache_ttl</code> is hit.</li>
+<li><code>target_memory_usage</code> sets a rough target for the desired memory usage of the caches.</li>
+<li><code>min_cache_ttl</code> sets a limit under which newer cache entries are not evicted and is only applied when
+caches are actively being evicted/<code>max_cache_memory_usage</code> has been exceeded. This is to protect hot caches
+from being emptied while Synapse is evicting due to memory.</li>
+</ul>
+</li>
 </ul>
 <p>Example configuration:</p>
 <pre><code class="language-yaml">caches:
   global_factor: 1.0
   per_cache_factors:
     get_users_who_share_room_with_user: 2.0
-  expire_caches: false
   sync_response_cache_duration: 2m
+  cache_autotuning:
+    max_cache_memory_usage: 1024M
+    target_cache_memory_usage: 758M
+    min_cache_ttl: 5m
 </code></pre>
 <h3 id="reloading-cache-factors"><a class="header" href="#reloading-cache-factors">Reloading cache factors</a></h3>
 <p>The cache factors (i.e. <code>caches.global_factor</code> and <code>caches.per_cache_factors</code>)  may be reloaded at any time by sending a
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