diff --git a/docs/content/configuration/caching.md b/docs/content/configuration/caching.md
index f1ca264ae10..ddee7c49736 100644
--- a/docs/content/configuration/caching.md
+++ b/docs/content/configuration/caching.md
@@ -24,7 +24,7 @@ for both broker and historical nodes, when defined in the common properties file
 
 #### Local Cache
 
-A simple in-memory LRU cache.
+A simple in-memory LRU cache. Local cache resides in JVM heap memory, so if you enable it, make sure you increase heap size accordingly.
 
 |Property|Description|Default|
 |--------|-----------|-------|
diff --git a/docs/content/operations/performance-faq.md b/docs/content/operations/performance-faq.md
index 37b04447647..e6f6ffff6d3 100644
--- a/docs/content/operations/performance-faq.md
+++ b/docs/content/operations/performance-faq.md
@@ -10,7 +10,7 @@ The size of the JVM heap really depends on the type of Druid node you are runnin
 
 [Broker nodes](../design/broker.html) uses the JVM heap mainly to merge results from historicals and real-times. Brokers also use off-heap memory and processing threads for groupBy queries. We recommend 20G-30G of heap here.
 
-[Historical nodes](../design/historical.html) use off-heap memory to store intermediate results, and by default, all segments are memory mapped before they can be queried. Typically, the more memory is available on a historical node, the more segments can be served without the possibility of data being paged on to disk. On historicals, the JVM heap is used for [GroupBy queries](../querying/groupbyquery.html), some data structures used for intermediate computation, and general processing. One way to calculate how much space there is for segments is: memory_for_segments = total_memory - heap - direct_memory - jvm_overhead.
+[Historical nodes](../design/historical.html) use off-heap memory to store intermediate results, and by default, all segments are memory mapped before they can be queried. Typically, the more memory is available on a historical node, the more segments can be served without the possibility of data being paged on to disk. On historicals, the JVM heap is used for [GroupBy queries](../querying/groupbyquery.html), some data structures used for intermediate computation, and general processing. One way to calculate how much space there is for segments is: memory_for_segments = total_memory - heap - direct_memory - jvm_overhead. Note that total_memory here refers to the memory available to the cgroup (if running on Linux), which for default cases is going to be all the system memory.
 
 We recommend 250mb * (processing.numThreads) for the heap.