Use a shared LevelDB block cache for LevelDB instances.

There will be one shared block cache for all users of
LevelDB::Init, and a separate one for All IndexedDB
instances. The default is 8MB, but it's 512KB for
low-memory Android devices.

Previously, each instance would get its own block cache, and use
the default LevelDB settings for such a cache, which is 8MB (*)

(*) https://cs.chromium.org/chromium/src/third_party/leveldatabase/src/include/leveldb/options.h?gsn=Options&l=96

Bug: 711518
Change-Id: I6a64467815489ae7695b8db9b9074170d9e56d94
Reviewed-on: https://chromium-review.googlesource.com/567583
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486934}

components/leveldb_proto/leveldb_database.cc

@@ -15,6 +15,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
+#include "base/sys_info.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/threading/thread_checker.h"
 #include "base/trace_event/memory_dump_manager.h"
@@ -86,16 +87,33 @@ bool LevelDB::InitWithOptions(const base::FilePath& database_dir,
   return false;
 }
 
+static size_t DefaultBlockCacheSize() {
+  if (base::SysInfo::IsLowEndDevice())
+    return 512 * 1024;  // 512KB
+  else
+    return 8 * 1024 * 1024;  // 8MB
+}
+
 bool LevelDB::Init(const leveldb_proto::Options& options) {
   leveldb::Options leveldb_options;
   leveldb_options.create_if_missing = true;
   leveldb_options.max_open_files = 0;  // Use minimum.
   leveldb_options.reuse_logs = leveldb_env::kDefaultLogReuseOptionValue;
+
+  static leveldb::Cache* default_block_cache =
+      leveldb::NewLRUCache(DefaultBlockCacheSize());
+
   if (options.write_buffer_size != 0)
     leveldb_options.write_buffer_size = options.write_buffer_size;
   if (options.read_cache_size != 0) {
     custom_block_cache_.reset(leveldb::NewLRUCache(options.read_cache_size));
     leveldb_options.block_cache = custom_block_cache_.get();
+  } else {
+    // By default, allocate a single block cache to be shared across
+    // all LevelDB instances created via this method.
+    // See also content/browser/indexed_db/leveldb/leveldb_database.cc,
+    // which has its own shared block cache for IndexedDB databases.
+    leveldb_options.block_cache = default_block_cache;
   }
   if (options.database_dir.empty()) {
     env_.reset(leveldb::NewMemEnv(leveldb::Env::Default()));

components/leveldb_proto/options.h

@@ -10,6 +10,9 @@
 namespace leveldb_proto {
 
 struct Options {
+  // If read_cache_size is specified, a segregated block cache will be
+  // created for this LevelDB instance. Otherwise a shared block cache
+  // will be used.
   Options(const base::FilePath& database_dir)
       : database_dir(database_dir), write_buffer_size(0), read_cache_size(0) {}
   Options(const base::FilePath& database_dir,

content/browser/indexed_db/leveldb/leveldb_database.cc

@@ -33,11 +33,11 @@
 #include "content/browser/indexed_db/leveldb/leveldb_write_batch.h"
 #include "third_party/leveldatabase/env_chromium.h"
 #include "third_party/leveldatabase/src/helpers/memenv/memenv.h"
+#include "third_party/leveldatabase/src/include/leveldb/cache.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 #include "third_party/leveldatabase/src/include/leveldb/env.h"
 #include "third_party/leveldatabase/src/include/leveldb/filter_policy.h"
 #include "third_party/leveldatabase/src/include/leveldb/slice.h"
-
 using base::StringPiece;
 
 namespace content {
@@ -117,6 +117,13 @@ void LevelDBDatabase::CloseDatabase() {
   }
 }
 
+static size_t DefaultBlockCacheSize() {
+  if (base::SysInfo::IsLowEndDevice())
+    return 512 * 1024;  // 512KB
+  else
+    return 8 * 1024 * 1024;  // 8MB
+}
+
 static leveldb::Status OpenDB(
     leveldb::Comparator* comparator,
     leveldb::Env* env,
@@ -139,6 +146,14 @@ static leveldb::Status OpenDB(
   options.max_open_files = 80;
   options.env = env;
 
+  // A shared block cache for all IndexedDB instances across all renderers.
+  // See also components/leveldb_proto/leveldb_database.cc, which has
+  // its own block cache for a different (internal use-cases) set of LevelDB
+  // instances.
+  static leveldb::Cache* default_block_cache =
+      leveldb::NewLRUCache(DefaultBlockCacheSize());
+  options.block_cache = default_block_cache;
+
   // ChromiumEnv assumes UTF8, converts back to FilePath before using.
   leveldb::DB* db_ptr = nullptr;
   leveldb::Status s = leveldb::DB::Open(options, path.AsUTF8Unsafe(), &db_ptr);