Add a field trial for using lower sqlite cache sizes.

chrome/browser/history/text_database.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits>
 #include <set>
 #include <string>
 
 #include "chrome/browser/history/text_database.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/string_number_conversions.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/diagnostics/sqlite_diagnostics.h"
+#include "chrome/browser/history/history_field_trial.h"
 #include "sql/statement.h"
 #include "sql/transaction.h"
 
 // There are two tables in each database, one full-text search (FTS) table which
 // indexes the contents and title of the pages. The other is a regular SQLITE
 // table which contains non-indexed information about the page. All columns of
 // a FTS table are indexed using the text search algorithm, which isn't what we
 // want for things like times. If this were in the FTS table, there would be
 // different words in the index for each time number.
 //
@@ skipping 103 matching lines @@
   // Set the database page size to something a little larger to give us
   // better performance (we're typically seek rather than bandwidth limited).
   // This only has an effect before any tables have been created, otherwise
   // this is a NOP. Must be a power of 2 and a max of 8192.
   db_.set_page_size(4096);
 
   // The default cache size is 2000 which give >8MB of data. Since we will often
   // have 2-3 of these objects, each with their own 8MB, this adds up very fast.
   // We therefore reduce the size so when there are multiple objects, we're not
   // too big.
-  db_.set_cache_size(512);
+  if (HistoryFieldTrial::IsLowMemFieldTrial()) {
+    // FTS does merges of 16 pages at a time, so we need a working set size
+    // somewhat greater than that to prevent too much thrashing.
+    db_.set_cache_size(128);
+  } else {
+    db_.set_cache_size(512);
+  }
 
   // Run the database in exclusive mode. Nobody else should be accessing the
   // database while we're running, and this will give somewhat improved perf.
   db_.set_exclusive_locking();
 
   // Attach the database to our index file.
   if (!db_.Open(file_name_))
     return false;
 
   // Meta table tracking version information.
@@ skipping 223 matching lines @@
   } else {
     // Since we got the results in order, we know the last item is the last
     // time we considered.
     *first_time_searched = results->back().time;
   }
 
   statement.Reset();
 }
 
 }  // namespace history