From 803e70160655f93a51df483a3c0fe7d418e46ae6 Mon Sep 17 00:00:00 2001
From: Mark Nelson <mnelson@redhat.com>
Date: Tue, 27 Jun 2017 08:15:03 -0500
Subject: [PATCH] kv/RocksDBStore: explicitly disable block_cache when set to
 0.

Signed-off-by: Mark Nelson <mnelson@redhat.com>
---
 src/kv/RocksDBStore.cc | 32 ++++++++++++++++++++------------
 src/kv/RocksDBStore.h  |  2 ++
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/kv/RocksDBStore.cc b/src/kv/RocksDBStore.cc
index aad274f5c71f5..01c2369ca6f0f 100644
--- a/src/kv/RocksDBStore.cc
+++ b/src/kv/RocksDBStore.cc
@@ -298,23 +298,31 @@ int RocksDBStore::do_open(ostream &out, bool create_if_missing)
   }
 
   // caches
-  if (!cache_size) {
+  if (!set_cache_flag) {
     cache_size = g_conf->rocksdb_cache_size;
   }
   uint64_t row_cache_size = cache_size * g_conf->rocksdb_cache_row_ratio;
   uint64_t block_cache_size = cache_size - row_cache_size;
-  if (g_conf->rocksdb_cache_type == "lru") {
-    bbt_opts.block_cache = rocksdb::NewLRUCache(
-      block_cache_size,
-      g_conf->rocksdb_cache_shard_bits);
-  } else if (g_conf->rocksdb_cache_type == "clock") {
-    bbt_opts.block_cache = rocksdb::NewClockCache(
-      block_cache_size,
-      g_conf->rocksdb_cache_shard_bits);
+
+  if (block_cache_size == 0) {
+    // disable block cache
+    dout(10) << __func__ << " block_cache_size " << block_cache_size
+             << ", setting no_block_cache " << dendl;
+    bbt_opts.no_block_cache = true;
   } else {
-    derr << "unrecognized rocksdb_cache_type '" << g_conf->rocksdb_cache_type
-	 << "'" << dendl;
-    return -EINVAL;
+    if (g_conf->rocksdb_cache_type == "lru") {
+      bbt_opts.block_cache = rocksdb::NewLRUCache(
+        block_cache_size,
+        g_conf->rocksdb_cache_shard_bits);
+    } else if (g_conf->rocksdb_cache_type == "clock") {
+      bbt_opts.block_cache = rocksdb::NewClockCache(
+        block_cache_size,
+        g_conf->rocksdb_cache_shard_bits);
+    } else {
+      derr << "unrecognized rocksdb_cache_type '" << g_conf->rocksdb_cache_type
+  	 << "'" << dendl;
+      return -EINVAL;
+    }
   }
   bbt_opts.block_size = g_conf->rocksdb_block_size;
 
diff --git a/src/kv/RocksDBStore.h b/src/kv/RocksDBStore.h
index c437badebabbb..321653448973f 100644
--- a/src/kv/RocksDBStore.h
+++ b/src/kv/RocksDBStore.h
@@ -76,6 +76,7 @@ class RocksDBStore : public KeyValueDB {
   string options_str;
 
   uint64_t cache_size = 0;
+  bool set_cache_flag = false;
 
   int do_open(ostream &out, bool create_if_missing);
 
@@ -439,6 +440,7 @@ err:
 
   int set_cache_size(uint64_t s) override {
     cache_size = s;
+    set_cache_flag = true;
     return 0;
   }
 
-- 
2.39.5