Tweak buffer size for APK checksumming.

Benchmark to calculate SHA256 over 1GB file:
    4K:  1529542318
    8K:  1101879125
    16K:  989211442
    32K:  783037993  ~20.8%
    64K:  742122399  ~5.2%
    128K: 723034565  ~4.2%
    256K: 716748703  ~0.8%
    512K: 718178800  ~-0.2%
    1M:   719738817

128K seems to be the sweet spot, with 256K being only marginally better and 512K is worse.

Bug: 196253439
Fixes: 196253439
Test: atest PackageManagerShellCommandTest PackageManagerShellCommandIncrementalTest IncrementalServiceTest PackageManagerServiceTest ChecksumsTest
Change-Id: I502e42652ed78f3eb843edc49d0b486552231a15

1 files changed, 9 insertions, 6 deletions

diff --git a/services/core/java/com/android/server/pm/ApkChecksums.java b/services/core/java/com/android/server/pm/ApkChecksums.java
index a44cad844202..aa467e782e84 100644
--- a/services/core/java/com/android/server/pm/ApkChecksums.java
+++ b/services/core/java/com/android/server/pm/ApkChecksums.java
@@ -64,7 +64,6 @@ import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.security.VerityUtils;
 import com.android.server.pm.parsing.pkg.AndroidPackage;
 
-import java.io.BufferedInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
@@ -724,16 +723,20 @@ public class ApkChecksums {
         }
     }
 
+    static final int MIN_BUFFER_SIZE = 4 * 1024;
+    static final int MAX_BUFFER_SIZE = 128 * 1024;
+
     private static byte[] getApkChecksum(File file, int type) {
-        try (FileInputStream fis = new FileInputStream(file);
-             BufferedInputStream bis = new BufferedInputStream(fis)) {
-            byte[] dataBytes = new byte[512 * 1024];
+        final int bufferSize = (int) Math.max(MIN_BUFFER_SIZE,
+                Math.min(MAX_BUFFER_SIZE, file.length()));
+        try (FileInputStream fis = new FileInputStream(file)) {
+            final byte[] buffer = new byte[bufferSize];
             int nread = 0;
 
             final String algo = getMessageDigestAlgoForChecksumKind(type);
             MessageDigest md = MessageDigest.getInstance(algo);
-            while ((nread = bis.read(dataBytes)) != -1) {
-                md.update(dataBytes, 0, nread);
+            while ((nread = fis.read(buffer)) != -1) {
+                md.update(buffer, 0, nread);
             }
 
             return md.digest();