Commit 627b331b authored Sep 17, 2010 by Vasu Nori

add new param to device config properties: db connection pool size

connection pool = number of database connections opened when the app opens
a database. These pooled connections are used by readers only and they
use the sqlite write-ahead-logging option to increase reader
concurrency.
The size of this connection pool depends on the number of CPUs, RAM etc.
On most single-core devices, this can be set to 1.
But on some multi-core devices with more RAM, pool size can be
more than 1.
On a device with more resources, here are the results of a test (in
coretests/src/android/database/sqlite/SQLiteDatabaseTest.java)
which measures the reader-parallelism achieved for different connection
pool sizes.
connpool-size = 1
  num xacts by writer = 467
  num-reads-in-xact/NOT-in-xact by reader1 = 1358/14542, by reader2 = 1431/14269
connpool-size = 2
  num xacts by writer = 473
  num-reads-in-xact/NOT-in-xact by reader1 = 5703/35227, by reader2 = 6222/35898
connpool-size = 3
  num xacts by writer = 542
  num-reads-in-xact/NOT-in-xact by reader1 = 6531/32329, by reader2 = 6252/32728
connpool-size = 4
  num xacts by writer = 578
  num-reads-in-xact/NOT-in-xact by reader1 = 6009/32701, by reader2 = 5977/32953
connpool-size = 5
  num xacts by writer = 547
  num-reads-in-xact/NOT-in-xact by reader1 = 6554/31186, by reader2 = 5318/31022
connpool-size = 6
  num xacts by writer = 534
  num-reads-in-xact/NOT-in-xact by reader1 = 5317/31463, by reader2 = 5413/31537
connpool-size = 7
  num xacts by writer = 549
  num-reads-in-xact/NOT-in-xact by reader1 = 5396/28004, by reader2 = 5214/28496

seems like connection pool size of 3 is optimal on this device.

Change-Id: I348ff5a31783c31b5e3e5ac78b7c2cea54ef114a

parent fa213d82

core/java/android/database/sqlite/DatabaseConnectionPool.java

+4 −7

Original line number	Diff line number	Diff line
		@@ -16,6 +16,7 @@

		package android.database.sqlite;

		import android.content.res.Resources;
		import android.os.SystemClock;
		import android.util.Log;

		@@ -31,13 +32,9 @@ import java.util.Random;

		private static final String TAG = "DatabaseConnectionPool";

		/** The default connection pool size. It is set based on the amount of memory the device has.
		* TODO: set this with 'a system call' which returns the amount of memory the device has
		*/
		private static final int DEFAULT_CONNECTION_POOL_SIZE = 1;

		/** the pool size set for this {@link SQLiteDatabase} */
		private volatile int mMaxPoolSize = DEFAULT_CONNECTION_POOL_SIZE;
		/** The default connection pool size. */
		private volatile int mMaxPoolSize =
		Resources.getSystem().getInteger(com.android.internal.R.integer.db_connection_pool_size);

		/** The connection pool objects are stored in this member.
		* TODO: revisit this data struct as the number of pooled connections increase beyond

core/res/res/values/config.xml

+4 −0

Original line number	Diff line number	Diff line
		@@ -416,4 +416,8 @@

		<!-- Enables SIP on WIFI only -->
		<bool name="config_sip_wifi_only">false</bool>

		<!-- Number of database connections opened and managed by framework layer
		to handle queries on each database. -->
		<integer name="db_connection_pool_size">1</integer>
		</resources>