diff --git a/conf/bookkeeper.conf b/conf/bookkeeper.conf
index 9df49d2596b54..da68a3d69bd6b 100644
--- a/conf/bookkeeper.conf
+++ b/conf/bookkeeper.conf
@@ -628,12 +628,15 @@ httpServerClass=org.apache.bookkeeper.http.vertx.VertxHttpServer
 
 # Size of Write Cache. Memory is allocated from JVM direct memory.
 # Write cache is used to buffer entries before flushing into the entry log
-# For good performance, it should be big enough to hold a sub
-dbStorage_writeCacheMaxSizeMb=512
+# For good performance, it should be big enough to hold a substantial amount
+# of entries in the flush interval
+#  By default it will be allocated to 1/4th of the available direct memory
+dbStorage_writeCacheMaxSizeMb=
 
 # Size of Read cache. Memory is allocated from JVM direct memory.
 # This read cache is pre-filled doing read-ahead whenever a cache miss happens
-dbStorage_readAheadCacheMaxSizeMb=256
+#  By default it will be allocated to 1/4th of the available direct memory
+dbStorage_readAheadCacheMaxSizeMb=
 
 # How many entries to pre-fill in cache after a read cache miss
 dbStorage_readAheadCacheBatchSize=1000
@@ -645,8 +648,8 @@ dbStorage_readAheadCacheBatchSize=1000
 # Size of RocksDB block-cache. For best performance, this cache
 # should be big enough to hold a significant portion of the index
 # database which can reach ~2GB in some cases
-# Default is 256 MBytes
-dbStorage_rocksDB_blockCacheSize=268435456
+# Default is to use 10% of the direct memory size
+dbStorage_rocksDB_blockCacheSize=
 
 # Other RocksDB specific tunables
 dbStorage_rocksDB_writeBufferSizeMB=64
diff --git a/conf/standalone.conf b/conf/standalone.conf
index 7187a95ec1e66..a6a26219b0470 100644
--- a/conf/standalone.conf
+++ b/conf/standalone.conf
@@ -477,12 +477,15 @@ ledgerStorageClass=org.apache.bookkeeper.bookie.storage.ldb.DbLedgerStorage
 
 # Size of Write Cache. Memory is allocated from JVM direct memory.
 # Write cache is used to buffer entries before flushing into the entry log
-# For good performance, it should be big enough to hold a sub
-dbStorage_writeCacheMaxSizeMb=256
+# For good performance, it should be big enough to hold a substantial amount
+# of entries in the flush interval
+# By default it will be allocated to 1/4th of the available direct memory
+dbStorage_writeCacheMaxSizeMb=
 
 # Size of Read cache. Memory is allocated from JVM direct memory.
 # This read cache is pre-filled doing read-ahead whenever a cache miss happens
-dbStorage_readAheadCacheMaxSizeMb=64
+# By default it will be allocated to 1/4th of the available direct memory
+dbStorage_readAheadCacheMaxSizeMb=
 
 # How many entries to pre-fill in cache after a read cache miss
 dbStorage_readAheadCacheBatchSize=1000
@@ -496,8 +499,8 @@ flushInterval=60000
 # Size of RocksDB block-cache. For best performance, this cache
 # should be big enough to hold a significant portion of the index
 # database which can reach ~2GB in some cases
-# Default is 16 MBytes
-dbStorage_rocksDB_blockCacheSize=16777216
+# Default is to use 10% of the direct memory size
+dbStorage_rocksDB_blockCacheSize=
 
 # Other RocksDB specific tunables
 dbStorage_rocksDB_writeBufferSizeMB=4
diff --git a/site2/docs/reference-configuration.md b/site2/docs/reference-configuration.md
index a783f3a75442f..d763e432c52c7 100644
--- a/site2/docs/reference-configuration.md
+++ b/site2/docs/reference-configuration.md
@@ -84,10 +84,10 @@ BookKeeper is a replicated log storage system that Pulsar uses for durable stora
 |useHostNameAsBookieID|Whether the bookie should use its hostname to register with the coordination service (e.g.: zookeeper service). When false, bookie will use its ipaddress for the registration.|false|
 |statsProviderClass||org.apache.bookkeeper.stats.prometheus.PrometheusMetricsProvider|
 |prometheusStatsHttpPort||8000|
-|dbStorage_writeCacheMaxSizeMb|Size of Write Cache. Memory is allocated from JVM direct memory. Write cache is used to buffer entries before flushing into the entry log For good performance, it should be big enough to hold a sub|512|
-|dbStorage_readAheadCacheMaxSizeMb|Size of Read cache. Memory is allocated from JVM direct memory. This read cache is pre-filled doing read-ahead whenever a cache miss happens|256|
+|dbStorage_writeCacheMaxSizeMb|Size of Write Cache. Memory is allocated from JVM direct memory. Write cache is used to buffer entries before flushing into the entry log For good performance, it should be big enough to hold a sub|25% of direct memory|
+|dbStorage_readAheadCacheMaxSizeMb|Size of Read cache. Memory is allocated from JVM direct memory. This read cache is pre-filled doing read-ahead whenever a cache miss happens|25% of direct memory|
 |dbStorage_readAheadCacheBatchSize|How many entries to pre-fill in cache after a read cache miss|1000|
-|dbStorage_rocksDB_blockCacheSize|Size of RocksDB block-cache. For best performance, this cache should be big enough to hold a significant portion of the index database which can reach ~2GB in some cases|268435456|
+|dbStorage_rocksDB_blockCacheSize|Size of RocksDB block-cache. For best performance, this cache should be big enough to hold a significant portion of the index database which can reach ~2GB in some cases|10% of direct memory|
 |dbStorage_rocksDB_writeBufferSizeMB||64|
 |dbStorage_rocksDB_sstSizeInMB||64|
 |dbStorage_rocksDB_blockSize||65536|