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Commit f859b257 authored by Piyush Mehrotra's avatar Piyush Mehrotra
Browse files

Control buffer size via server flags when writing to pipes in Full Backup flow. 

Reasoning behind making buffer size configurable -
- In PerformFullTransportBackupTask (PFTBT) ->
    * PFTBT calls Transport#sendBackupData() everytime it writes buffer to the write end of the pipe (which is then read by the transport). That method is invoked through binder, which introduces some overhead. Current buffer size of 8KB means that for 25MB of backup data, PFTBT does a minimum of 3200 binder calls. Increasing the buffer size to 64KB, the number of binder call reduces to 400.
- In FullBackupUtils ->
    * FullBackupUtils#routeSocketDataToOutput() routes the data from BackupAgent to FullBackupEngine. Linux pipe2 implementation of Android has default size of 64KB. Increasing the buffer size in FullBackupUtils from 32KB to 64KB will result in optimal performance for piping the data, as buffer size will match input pipe's buffer.

Bug: b/265976737
Test: atest BackupAndRestoreFeatureFlagsTest
    - Manual testing for the performance impact
Change-Id: I729e0a5857e254eb9451eecf6fd9e58ac0511eb8
parent 796c571a

services/backup/java/com/android/server/backup/BackupAndRestoreFeatureFlags.java

+25 −0
Original line number Diff line number Diff line
@@ -52,4 +52,29 @@ public class BackupAndRestoreFeatureFlags { 
                /* name= */ "backup_transport_callback_timeout_millis",

                /* defaultValue= */ 300000); // 5 minutes

    }



    /**

     * Retrieves the value of the flag "full_backup_write_to_transport_buffer_size_bytes".

     * The returned value is max size of a chunk of backup data that is sent to the transport.

     */

    @RequiresPermission(Manifest.permission.READ_DEVICE_CONFIG)

    public static int getFullBackupWriteToTransportBufferSizeBytes() {

        return DeviceConfig.getInt(

                NAMESPACE,

                /* name= */ "full_backup_write_to_transport_buffer_size_bytes",

                /* defaultValue= */ 8 * 1024); // 8 KB

    }



    /**

     * Retrieves the value of the flag "full_backup_utils_route_buffer_size_bytes".

     * The returned value is max size of a chunk of backup data that routed from write end of

     * pipe from BackupAgent, to read end of pipe to Full Backup Task (PFTBT).

     */

    @RequiresPermission(Manifest.permission.READ_DEVICE_CONFIG)

    public static int getFullBackupUtilsRouteBufferSizeBytes() {

        return DeviceConfig.getInt(

                NAMESPACE,

                /* name= */ "full_backup_utils_route_buffer_size_bytes",

                /* defaultValue= */ 32 * 1024); // 32 KB

    }

}

services/backup/java/com/android/server/backup/fullbackup/PerformFullTransportBackupTask.java

+4 −2
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ import android.util.Slog; 


import com.android.server.EventLogTags;

import com.android.server.backup.BackupAgentTimeoutParameters;

import com.android.server.backup.BackupAndRestoreFeatureFlags;

import com.android.server.backup.BackupRestoreTask;

import com.android.server.backup.FullBackupJob;

import com.android.server.backup.OperationStorage;
@@ -142,7 +143,6 @@ public class PerformFullTransportBackupTask extends FullBackupTask implements Ba 
    }



    private static final String TAG = "PFTBT";



    private UserBackupManagerService mUserBackupManagerService;

    private final Object mCancelLock = new Object();
@@ -388,7 +388,9 @@ public class PerformFullTransportBackupTask extends FullBackupTask implements Ba 


            // Set up to send data to the transport

            final int N = mPackages.size();

            final byte[] buffer = new byte[8192];

            final int chunkSizeInBytes =

                    BackupAndRestoreFeatureFlags.getFullBackupWriteToTransportBufferSizeBytes();

            final byte[] buffer = new byte[chunkSizeInBytes];

            for (int i = 0; i < N; i++) {

                mBackupRunner = null;

                PackageInfo currentPackage = mPackages.get(i);

services/backup/java/com/android/server/backup/utils/FullBackupUtils.java

+7 −3
Original line number Diff line number Diff line
@@ -21,6 +21,8 @@ import static com.android.server.backup.BackupManagerService.TAG; 
import android.os.ParcelFileDescriptor;

import android.util.Slog;



import com.android.server.backup.BackupAndRestoreFeatureFlags;



import java.io.DataInputStream;

import java.io.EOFException;

import java.io.FileInputStream;
@@ -31,8 +33,9 @@ import java.io.OutputStream; 
 * Low-level utility methods for full backup.

 */

public class FullBackupUtils {



    /**

     * Reads data from pipe and writes it to the stream in chunks of up to 32KB.

     * Reads data from pipe and writes it to the stream.

     *

     * @param inPipe - pipe to read the data from.

     * @param out - stream to write the data to.
@@ -43,8 +46,9 @@ public class FullBackupUtils { 
        // We do not take close() responsibility for the pipe FD

        FileInputStream raw = new FileInputStream(inPipe.getFileDescriptor());

        DataInputStream in = new DataInputStream(raw);



        byte[] buffer = new byte[32 * 1024];

        final int chunkSizeInBytes =

                BackupAndRestoreFeatureFlags.getFullBackupUtilsRouteBufferSizeBytes();

        byte[] buffer = new byte[chunkSizeInBytes];

        int chunkTotal;

        while ((chunkTotal = in.readInt()) > 0) {

            while (chunkTotal > 0) {

services/tests/mockingservicestests/src/com/android/server/backup/BackupAndRestoreFeatureFlagsTest.java

+38 −4
Original line number Diff line number Diff line
@@ -46,8 +46,9 @@ public class BackupAndRestoreFeatureFlagsTest { 


    @Test

    public void getBackupTransportFutureTimeoutMillis_set_returnsSetValue() {

        DeviceConfig.setProperty("backup_and_restore", "backup_transport_future_timeout_millis",

                "1234", false);

        DeviceConfig.setProperty(/*namespace=*/ "backup_and_restore",

                /*name=*/ "backup_transport_future_timeout_millis",

                /*value=*/ "1234", /*makeDefault=*/ false);



        assertThat(

                BackupAndRestoreFeatureFlags.getBackupTransportFutureTimeoutMillis()).isEqualTo(
@@ -63,11 +64,44 @@ public class BackupAndRestoreFeatureFlagsTest { 


    @Test

    public void getBackupTransportCallbackTimeoutMillis_set_returnsSetValue() {

        DeviceConfig.setProperty("backup_and_restore", "backup_transport_callback_timeout_millis",

                "5678", false);

        DeviceConfig.setProperty(/*namespace=*/ "backup_and_restore",

                /*name=*/ "backup_transport_callback_timeout_millis",

                /*value=*/ "5678", /*makeDefault=*/ false);



        assertThat(

                BackupAndRestoreFeatureFlags.getBackupTransportCallbackTimeoutMillis()).isEqualTo(

                5678);

    }



    @Test

    public void getFullBackupWriteToTransportBufferSizeBytes_notSet_returnsDefault() {

        assertThat(BackupAndRestoreFeatureFlags.getFullBackupWriteToTransportBufferSizeBytes())

                .isEqualTo(8 * 1024);

    }



    @Test

    public void getFullBackupWriteToTransportBufferSizeBytes_set_returnsSetValue() {

        DeviceConfig.setProperty(/*namespace=*/ "backup_and_restore",

                /*name=*/ "full_backup_write_to_transport_buffer_size_bytes",

                /*value=*/ "5678", /*makeDefault=*/ false);



        assertThat(BackupAndRestoreFeatureFlags.getFullBackupWriteToTransportBufferSizeBytes())

                .isEqualTo(5678);

    }



    @Test

    public void getFullBackupUtilsRouteBufferSizeBytes_notSet_returnsDefault() {

        assertThat(BackupAndRestoreFeatureFlags.getFullBackupUtilsRouteBufferSizeBytes())

                .isEqualTo(32 * 1024);

    }



    @Test

    public void getFullBackupUtilsRouteBufferSizeBytes_set_returnsSetValue() {

        DeviceConfig.setProperty(/*namespace=*/ "backup_and_restore",

                /*name=*/ "full_backup_utils_route_buffer_size_bytes",

                /*value=*/ "5678", /*makeDefault=*/ false);



        assertThat(BackupAndRestoreFeatureFlags.getFullBackupUtilsRouteBufferSizeBytes())

                .isEqualTo(5678);

    }

}