commit 012ab8e9faf8b2a641c8c5082987d07163fec0e9
author Daniel Colascione <dancol@google.com> Mon Oct 07 14:18:09 2019 -0700
committer Daniel Colascione <dancol@google.com> Mon Oct 07 16:20:06 2019 -0700
tree bbcceee36b81ea049e1930ad055bae12e8a979a9
parent ff3cf4315ac9c4364a05da2e61ad9caffff4ca45

Mark common android.os.Parcel methods as FastNative

Mark the marshaling functions for non-primitive parameters as being
@FastNative: they're all expected to complete quickly.

According to the table in CriticalNative.java, the difference between
a regular JNI call and a FastNative call is about 80ns, so this change
should shave about 160ns per non-primitive parameter off the latency
of a binder transaction. The actual savings will be greater as we also
use these Parcel methods to marshal and unmarshal complex objects like
PackageInfo sent as objects over Binder.

Bug: 142271139
Test: boots
Change-Id: I85c3ee8498640193b9c0777c8c5e7eb349c7b23c

core/java/android/os/Parcel.java

diff --git a/core/java/android/os/Parcel.java b/core/java/android/os/Parcel.java
index 50487e9..783ab44 100644
--- a/core/java/android/os/Parcel.java
+++ b/core/java/android/os/Parcel.java
@@ -305,8 +305,11 @@
     private static native void nativeWriteFloat(long nativePtr, float val);
     @FastNative
     private static native void nativeWriteDouble(long nativePtr, double val);
+    @FastNative
     static native void nativeWriteString(long nativePtr, String val);
+    @FastNative
     private static native void nativeWriteStrongBinder(long nativePtr, IBinder val);
+    @FastNative
     private static native long nativeWriteFileDescriptor(long nativePtr, FileDescriptor val);
 
     private static native byte[] nativeCreateByteArray(long nativePtr);
@@ -320,8 +323,11 @@
     private static native float nativeReadFloat(long nativePtr);
     @CriticalNative
     private static native double nativeReadDouble(long nativePtr);
+    @FastNative
     static native String nativeReadString(long nativePtr);
+    @FastNative
     private static native IBinder nativeReadStrongBinder(long nativePtr);
+    @FastNative
     private static native FileDescriptor nativeReadFileDescriptor(long nativePtr);
 
     private static native long nativeCreate();

core/jni/android_os_Parcel.cpp

diff --git a/core/jni/android_os_Parcel.cpp b/core/jni/android_os_Parcel.cpp
index d80c071..483b455 100644
--- a/core/jni/android_os_Parcel.cpp
+++ b/core/jni/android_os_Parcel.cpp
@@ -721,8 +721,11 @@
     {"nativeWriteFloat",          "(JF)V", (void*)android_os_Parcel_writeFloat},
     // @FastNative
     {"nativeWriteDouble",         "(JD)V", (void*)android_os_Parcel_writeDouble},
+    // @FastNative
     {"nativeWriteString",         "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeString},
+    // @FastNative
     {"nativeWriteStrongBinder",   "(JLandroid/os/IBinder;)V", (void*)android_os_Parcel_writeStrongBinder},
+    // @FastNative
     {"nativeWriteFileDescriptor", "(JLjava/io/FileDescriptor;)J", (void*)android_os_Parcel_writeFileDescriptor},
 
     {"nativeCreateByteArray",     "(J)[B", (void*)android_os_Parcel_createByteArray},
@@ -736,8 +739,11 @@
     {"nativeReadFloat",           "(J)F", (void*)android_os_Parcel_readFloat},
     // @CriticalNative
     {"nativeReadDouble",          "(J)D", (void*)android_os_Parcel_readDouble},
+    // @FastNative
     {"nativeReadString",          "(J)Ljava/lang/String;", (void*)android_os_Parcel_readString},
+    // @FastNative
     {"nativeReadStrongBinder",    "(J)Landroid/os/IBinder;", (void*)android_os_Parcel_readStrongBinder},
+    // @FastNative
     {"nativeReadFileDescriptor",  "(J)Ljava/io/FileDescriptor;", (void*)android_os_Parcel_readFileDescriptor},
 
     {"nativeCreate",              "()J", (void*)android_os_Parcel_create},

core/jni/android_util_Binder.cpp

diff --git a/core/jni/android_util_Binder.cpp b/core/jni/android_util_Binder.cpp
index 0afbaa0e..e406e22 100644
--- a/core/jni/android_util_Binder.cpp
+++ b/core/jni/android_util_Binder.cpp
@@ -697,6 +697,9 @@
 // same IBinder, and the original BinderProxy is still alive, return the same BinderProxy.
 jobject javaObjectForIBinder(JNIEnv* env, const sp<IBinder>& val)
 {
+    // N.B. This function is called from a @FastNative JNI method, so don't take locks around
+    // calls to Java code or block the calling thread for a long time for any reason.
+
     if (val == NULL) return NULL;
 
     if (val->checkSubclass(&gBinderOffsets)) {