Be more elaborate in background GC config example

Author: michaelklishin

docs/rabbitmq.conf.example

@@ -380,11 +380,18 @@
 ##
 # queue_index_embed_msgs_below = 4kb
 
-## Whether or not to enable background GC.
+## Whether or not to enable background periodic GC of all
+## Erlang processes in "waiting" state.
+##
+## Disabling background GC may reduce latency for client operations,
+## keeping it enabled may reduce median RAM usage.
 ##
 # background_gc_enabled = true
 
-## Interval (in milliseconds) at which we run background GC.
+## Target (desired) interval (in milliseconds) at which we run background GC.
+## The actual interval will vary depending on how long it takes to execute
+## the operation (can be higher than this interval). Values less than
+## 30000 milliseconds are not recommended.
 ##
 # background_gc_target_interval = 60000
 
@@ -623,7 +630,7 @@
 
 ## File rotation config. No rotation by defualt.
 ## DO NOT SET rotation date to ''. Leave unset if require "" value
-# log.file.rotation.date = $D0 
+# log.file.rotation.date = $D0
 # log.file.rotation.size = 0
 
 

docs/rabbitmq.config.example

@@ -333,11 +333,18 @@
    %%
    %% {queue_index_embed_msgs_below, 4096},
 
-   %% Whether or not to enable background GC.
+   %% Whether or not to enable background periodic GC of all
+   %% Erlang processes in "waiting" state.
+   %%
+   %% Disabling background GC may reduce latency for client operations,
+   %% keeping it enabled may reduce median RAM usage.
    %%
    %% {background_gc_enabled, true},
    %%
-   %% Interval (in milliseconds) at which we run background GC.
+   %% Target (desired) interval (in milliseconds) at which we run background GC.
+   %% The actual interval will vary depending on how long it takes to execute
+   %% the operation (can be higher than this interval). Values less than
+   %% 30000 milliseconds are not recommended.
    %%
    %% {background_gc_target_interval, 60000}