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

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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
This commit is contained in:
Vasu Nori
2010-09-17 11:20:20 -07:00
parent fa213d82a9
commit 627b331b32
2 changed files with 8 additions and 7 deletions
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11
core/java/android/database/sqlite/DatabaseConnectionPool.java
View File

@@ -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

4
core/res/res/values/config.xml
View File

@@ -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>