Increase page size for SyncData DB from 4K to maximum

supported 32K using finch experiment.

BUG=464063

Review URL: https://codereview.chromium.org/1016563005

Cr-Commit-Position: refs/heads/master@{#321529}

5 files changed, 80 insertions, 4 deletions

diff --git a/sync/syncable/deferred_on_disk_directory_backing_store.cc b/sync/syncable/deferred_on_disk_directory_backing_store.cc
index fbb7845..aa8c1ab 100644
--- a/sync/syncable/deferred_on_disk_directory_backing_store.cc
+++ b/sync/syncable/deferred_on_disk_directory_backing_store.cc
@@ -39,7 +39,7 @@ bool DeferredOnDiskDirectoryBackingStore::SaveChanges(
     // Reopen DB on disk.
     db_.reset(new sql::Connection);
     db_->set_exclusive_locking();
-    db_->set_page_size(4096);
+    db_->set_page_size(databasePageSize_);
     if (!db_->Open(backing_filepath_) || !InitializeTables())
       return false;
 
diff --git a/sync/syncable/directory_backing_store.cc b/sync/syncable/directory_backing_store.cc
index 9d18a2d..772ced4 100644
--- a/sync/syncable/directory_backing_store.cc
+++ b/sync/syncable/directory_backing_store.cc
@@ -10,6 +10,7 @@
 
 #include "base/base64.h"
 #include "base/logging.h"
+#include "base/metrics/field_trial.h"
 #include "base/rand_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/time/time.h"
@@ -175,8 +176,9 @@ DirectoryBackingStore::DirectoryBackingStore(const string& dir_name)
     dir_name_(dir_name),
     needs_column_refresh_(false) {
   db_->set_histogram_tag("SyncDirectory");
-  db_->set_page_size(4096);
   db_->set_cache_size(32);
+  databasePageSize_ = IsSyncBackingDatabase32KEnabled() ? 32768 : 4096;
+  db_->set_page_size(databasePageSize_);
 }
 
 DirectoryBackingStore::DirectoryBackingStore(const string& dir_name,
@@ -308,6 +310,11 @@ bool DirectoryBackingStore::SaveChanges(
 }
 
 bool DirectoryBackingStore::InitializeTables() {
+  int page_size = 0;
+  if (IsSyncBackingDatabase32KEnabled() && GetDatabasePageSize(&page_size) &&
+      page_size == 4096) {
+    IncreasePageSizeTo32K();
+  }
   sql::Transaction transaction(db_.get());
   if (!transaction.Begin())
     return false;
@@ -1592,5 +1599,35 @@ void DirectoryBackingStore::PrepareSaveEntryStatement(
       base::StringPrintf(query.c_str(), "metas").c_str()));
 }
 
+// Get page size for the database.
+bool DirectoryBackingStore::GetDatabasePageSize(int* page_size) {
+  sql::Statement s(db_->GetUniqueStatement("PRAGMA page_size"));
+  if (!s.Step())
+    return false;
+  *page_size = s.ColumnInt(0);
+  return true;
+}
+
+bool DirectoryBackingStore::IsSyncBackingDatabase32KEnabled() {
+  const std::string group_name =
+      base::FieldTrialList::FindFullName("SyncBackingDatabase32K");
+  return group_name == "Enabled";
+}
+
+bool DirectoryBackingStore::IncreasePageSizeTo32K() {
+  if (!db_->Execute("PRAGMA page_size=32768;") || !Vacuum()) {
+    return false;
+  }
+  return true;
+}
+
+bool DirectoryBackingStore::Vacuum() {
+  DCHECK_EQ(db_->transaction_nesting(), 0);
+  if (!db_->Execute("VACUUM;")) {
+    return false;
+  }
+  return true;
+}
+
 }  // namespace syncable
 }  // namespace syncer
diff --git a/sync/syncable/directory_backing_store.h b/sync/syncable/directory_backing_store.h
index 36a2f0a..7992037 100644
--- a/sync/syncable/directory_backing_store.h
+++ b/sync/syncable/directory_backing_store.h
@@ -44,6 +44,10 @@ struct ColumnSpec;
 // in tests.  The concrete class used in non-test scenarios is
 // OnDiskDirectoryBackingStore.
 class SYNC_EXPORT_PRIVATE DirectoryBackingStore : public base::NonThreadSafe {
+  friend class DirectoryBackingStoreTest;
+  FRIEND_TEST_ALL_PREFIXES(DirectoryBackingStoreTest,
+                           IncreaseDatabasePageSizeFrom4KTo32K);
+
  public:
   explicit DirectoryBackingStore(const std::string& dir_name);
   virtual ~DirectoryBackingStore();
@@ -145,6 +149,12 @@ class SYNC_EXPORT_PRIVATE DirectoryBackingStore : public base::NonThreadSafe {
   bool SetVersion(int version);
   int GetVersion();
 
+  bool GetDatabasePageSize(int* page_size);
+  bool IsSyncBackingDatabase32KEnabled();
+  bool IncreasePageSizeTo32K();
+  bool Vacuum();
+  int databasePageSize_;
+
   bool MigrateToSpecifics(const char* old_columns,
                           const char* specifics_column,
                           void(*handler_function) (
diff --git a/sync/syncable/directory_backing_store_unittest.cc b/sync/syncable/directory_backing_store_unittest.cc
index 7394b0d..f8b5434 100644
--- a/sync/syncable/directory_backing_store_unittest.cc
+++ b/sync/syncable/directory_backing_store_unittest.cc
@@ -18,6 +18,7 @@
 #include "sync/internal_api/public/base/node_ordinal.h"
 #include "sync/protocol/bookmark_specifics.pb.h"
 #include "sync/protocol/sync.pb.h"
+#include "sync/syncable/directory.h"
 #include "sync/syncable/directory_backing_store.h"
 #include "sync/syncable/on_disk_directory_backing_store.h"
 #include "sync/syncable/syncable-inl.h"
@@ -3966,5 +3967,33 @@ TEST_F(DirectoryBackingStoreTest, GenerateCacheGUID) {
   EXPECT_NE(guid1, guid2);
 }
 
+TEST_F(DirectoryBackingStoreTest, IncreaseDatabasePageSizeFrom4KTo32K) {
+  sql::Connection connection;
+  ASSERT_TRUE(connection.Open(GetDatabasePath()));
+
+  SetUpCurrentDatabaseAndCheckVersion(&connection);
+  scoped_ptr<TestDirectoryBackingStore> dbs(
+      new TestDirectoryBackingStore(GetUsername(), &connection));
+  Directory::MetahandlesMap handles_map;
+  JournalIndex delete_journals;
+  MetahandleSet metahandles_to_purge;
+  Directory::KernelLoadInfo kernel_load_info;
+  STLValueDeleter<Directory::MetahandlesMap> index_deleter(&handles_map);
+
+  DirOpenResult open_result = dbs->Load(
+      &handles_map, &delete_journals, &metahandles_to_purge, &kernel_load_info);
+  EXPECT_EQ(open_result, OPENED);
+
+  // Check if update is successful.
+  int pageSize = 0;
+  dbs->GetDatabasePageSize(&pageSize);
+  EXPECT_TRUE(32768 != pageSize);
+  dbs->db_->set_page_size(32768);
+  dbs->IncreasePageSizeTo32K();
+  pageSize = 0;
+  dbs->GetDatabasePageSize(&pageSize);
+  EXPECT_EQ(32768, pageSize);
+}
+
 }  // namespace syncable
 }  // namespace syncer
diff --git a/sync/syncable/on_disk_directory_backing_store.cc b/sync/syncable/on_disk_directory_backing_store.cc
index dcbaedd..834db69 100644
--- a/sync/syncable/on_disk_directory_backing_store.cc
+++ b/sync/syncable/on_disk_directory_backing_store.cc
@@ -29,7 +29,7 @@ OnDiskDirectoryBackingStore::OnDiskDirectoryBackingStore(
       allow_failure_for_test_(false),
       backing_filepath_(backing_filepath) {
   db_->set_exclusive_locking();
-  db_->set_page_size(4096);
+  db_->set_page_size(databasePageSize_);
 }
 
 OnDiskDirectoryBackingStore::~OnDiskDirectoryBackingStore() { }
@@ -85,7 +85,7 @@ DirOpenResult OnDiskDirectoryBackingStore::Load(
   // brittle.  Either have a helper to set these up (or generate a new
   // connection), or add something like Reset() to sql::Connection.
   db_->set_exclusive_locking();
-  db_->set_page_size(4096);
+  db_->set_page_size(databasePageSize_);
   db_->set_histogram_tag("SyncDirectory");
   base::DeleteFile(backing_filepath_, false);