Add config flags to allow for cache auto-tuning (#12701)

1 files changed, 18 insertions, 0 deletions

diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml

index 03a0f6314c..05a3606da0 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -784,6 +784,24 @@ caches:
   #
   #cache_entry_ttl: 30m
 
+  # This flag enables cache autotuning, and is further specified by the sub-options `max_cache_memory_usage`,
+  # `target_cache_memory_usage`, `min_cache_ttl`. These flags work in conjunction with each other to maintain
+  # a balance between cache memory usage and cache entry availability. You must be using jemalloc to utilize
+  # this option, and all three of the options must be specified for this feature to work.
+  #cache_autotuning:
+    # This flag sets a ceiling on 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 `target_memory_usage`, set in
+    # the flag below, or until the `min_cache_ttl` is hit.
+    #max_cache_memory_usage: 1024M
+
+    # This flag sets a rough target for the desired memory usage of the caches.
+    #target_cache_memory_usage: 758M
+
+    # 'min_cache_ttl` sets a limit under which newer cache entries are not evicted and is only applied when
+    # caches are actively being evicted/`max_cache_memory_usage` has been exceeded. This is to protect hot caches
+    # from being emptied while Synapse is evicting due to memory.
+    #min_cache_ttl: 5m
+
   # Controls how long the results of a /sync request are cached for after
   # a successful response is returned. A higher duration can help clients with
   # intermittent connections, at the cost of higher memory usage.