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Commit d387e79a authored by Jeff Sharkey's avatar Jeff Sharkey
Browse files

Offer to write Strings through Parcels as UTF-8. 

Recently while investigating some Binder limits, I discovered that
we're still sending Strings across Binder as UTF-16, which is very
wasteful for two reasons:

1. The majority of data flowing through APIs like PackageManager is
already limited to US-ASCII, and by sending UTF-16 we're wasting
half of our transactions on null-byte overhead.

2. Internally ART is already "compressing" simple strings by storing
them as US-ASCII instead of UTF-16, meaning every time we want to
write a simple string to Binder, we're forced to first inflate it
to UTF-16.

This change first updates Parcel.cpp to accept char* UTF-8 strings,
similar to how it accepts char16_t* for UTF-16.  It then offers
both UTF-8 and UTF-16 variants to Parcel.java via JNI.  We also
update the String8 handling to behave identical to String16.

This change adds benchmarking to show that these new methods are
about 50% faster for US-ASCII strings, and about 68% faster for
complex strings that reference higher Unicode planes.  (So an
improvement in both cases!)

Bug: 154436100
Test: atest FrameworksCoreTests:ParcelTest
Test: make core-libart conscrypt okhttp bouncycastle vogar caliper && vogar --mode app_process --benchmark frameworks/base/core/tests/benchmarks/src/android/os/ParcelStringBenchmark.java
Change-Id: I22a11d3497486d922ec8e14c85df66ca096b8f2a
parent 6d187276

core/java/android/content/pm/PackageParserCacheHelper.java

+20 −2
Original line number Original line Diff line number Diff line
@@ -78,10 +78,19 @@ public class PackageParserCacheHelper { 
        /**

        /**

         * Read an string index from a parcel, and returns the corresponding string from the pool.

         * Read an string index from a parcel, and returns the corresponding string from the pool.

         */

         */

        @Override

        public String readString(Parcel p) {

        public String readString(Parcel p) {

            return mStrings.get(p.readInt());

            return mStrings.get(p.readInt());

        }

        }



        @Override

        public String readString8(Parcel p) {

            return readString(p);

        }



        @Override

        public String readString16(Parcel p) {

            return readString(p);

        }

    }

    }





    /**

    /**
@@ -110,7 +119,6 @@ public class PackageParserCacheHelper { 
         * Instead of writing a string directly to a parcel, this method adds it to the pool,

         * Instead of writing a string directly to a parcel, this method adds it to the pool,

         * and write the index in the pool to the parcel.

         * and write the index in the pool to the parcel.

         */

         */

        @Override

        public void writeString(Parcel p, String s) {

        public void writeString(Parcel p, String s) {

            final Integer cur = mIndexes.get(s);

            final Integer cur = mIndexes.get(s);

            if (cur != null) {

            if (cur != null) {
@@ -133,6 +141,16 @@ public class PackageParserCacheHelper { 
            }

            }

        }

        }





        @Override

        public void writeString8(Parcel p, String s) {

            writeString(p, s);

        }



        @Override

        public void writeString16(Parcel p, String s) {

            writeString(p, s);

        }



        /**

        /**

         * Closes a parcel by appending the string pool at the end and updating the pool offset,

         * Closes a parcel by appending the string pool at the end and updating the pool offset,

         * which it assumes is at the first byte.  It also uninstalls itself as a read-write helper.

         * which it assumes is at the first byte.  It also uninstalls itself as a read-write helper.

core/java/android/os/Parcel.java

+63 −12
Original line number Original line Diff line number Diff line
@@ -307,7 +307,9 @@ public final class Parcel { 
    @FastNative

    @FastNative

    private static native void nativeWriteDouble(long nativePtr, double val);

    private static native void nativeWriteDouble(long nativePtr, double val);

    @FastNative

    @FastNative

    static native void nativeWriteString(long nativePtr, String val);

    private static native void nativeWriteString8(long nativePtr, String val);

    @FastNative

    private static native void nativeWriteString16(long nativePtr, String val);

    @FastNative

    @FastNative

    private static native void nativeWriteStrongBinder(long nativePtr, IBinder val);

    private static native void nativeWriteStrongBinder(long nativePtr, IBinder val);

    @FastNative

    @FastNative
@@ -325,7 +327,9 @@ public final class Parcel { 
    @CriticalNative

    @CriticalNative

    private static native double nativeReadDouble(long nativePtr);

    private static native double nativeReadDouble(long nativePtr);

    @FastNative

    @FastNative

    static native String nativeReadString(long nativePtr);

    private static native String nativeReadString8(long nativePtr);

    @FastNative

    private static native String nativeReadString16(long nativePtr);

    @FastNative

    @FastNative

    private static native IBinder nativeReadStrongBinder(long nativePtr);

    private static native IBinder nativeReadStrongBinder(long nativePtr);

    @FastNative

    @FastNative
@@ -386,8 +390,12 @@ public final class Parcel { 
         * must use {@link #writeStringNoHelper(String)} to avoid

         * must use {@link #writeStringNoHelper(String)} to avoid

         * infinity recursive calls.

         * infinity recursive calls.

         */

         */

        public void writeString(Parcel p, String s) {

        public void writeString8(Parcel p, String s) {

            nativeWriteString(p.mNativePtr, s);

            p.writeString8NoHelper(s);

        }



        public void writeString16(Parcel p, String s) {

            p.writeString16NoHelper(s);

        }

        }





        /**

        /**
@@ -395,8 +403,12 @@ public final class Parcel { 
         * must use {@link #readStringNoHelper()} to avoid

         * must use {@link #readStringNoHelper()} to avoid

         * infinity recursive calls.

         * infinity recursive calls.

         */

         */

        public String readString(Parcel p) {

        public String readString8(Parcel p) {

            return nativeReadString(p.mNativePtr);

            return p.readString8NoHelper();

        }



        public String readString16(Parcel p) {

            return p.readString16NoHelper();

        }

        }

    }

    }
@@ -759,7 +771,17 @@ public final class Parcel { 
     * growing dataCapacity() if needed.

     * growing dataCapacity() if needed.

     */

     */

    public final void writeString(@Nullable String val) {

    public final void writeString(@Nullable String val) {

        mReadWriteHelper.writeString(this, val);

        writeString16(val);

    }



    /** {@hide} */

    public final void writeString8(@Nullable String val) {

        mReadWriteHelper.writeString8(this, val);

    }



    /** {@hide} */

    public final void writeString16(@Nullable String val) {

        mReadWriteHelper.writeString16(this, val);

    }

    }





    /**

    /**
@@ -770,7 +792,17 @@ public final class Parcel { 
     * @hide

     * @hide

     */

     */

    public void writeStringNoHelper(@Nullable String val) {

    public void writeStringNoHelper(@Nullable String val) {

        nativeWriteString(mNativePtr, val);

        writeString16NoHelper(val);

    }



    /** {@hide} */

    public void writeString8NoHelper(@Nullable String val) {

        nativeWriteString8(mNativePtr, val);

    }



    /** {@hide} */

    public void writeString16NoHelper(@Nullable String val) {

        nativeWriteString16(mNativePtr, val);

    }

    }





    /**

    /**
@@ -2337,7 +2369,17 @@ public final class Parcel { 
     */

     */

    @Nullable

    @Nullable

    public final String readString() {

    public final String readString() {

        return mReadWriteHelper.readString(this);

        return readString16();

    }



    /** {@hide} */

    public final @Nullable String readString8() {

        return mReadWriteHelper.readString8(this);

    }



    /** {@hide} */

    public final @Nullable String readString16() {

        return mReadWriteHelper.readString16(this);

    }

    }





    /**

    /**
@@ -2347,9 +2389,18 @@ public final class Parcel { 
     *

     *

     * @hide

     * @hide

     */

     */

    @Nullable

    public @Nullable String readStringNoHelper() {

    public String readStringNoHelper() {

        return readString16NoHelper();

        return nativeReadString(mNativePtr);

    }



    /** {@hide} */

    public @Nullable String readString8NoHelper() {

        return nativeReadString8(mNativePtr);

    }



    /** {@hide} */

    public @Nullable String readString16NoHelper() {

        return nativeReadString16(mNativePtr);

    }

    }





    /**

    /**

core/jni/android_os_Parcel.cpp

+43 −4
Original line number Original line Diff line number Diff line
@@ -273,7 +273,28 @@ static void android_os_Parcel_writeDouble(JNIEnv* env, jclass clazz, jlong nativ 
    }

    }

}

}





static void android_os_Parcel_writeString(JNIEnv* env, jclass clazz, jlong nativePtr, jstring val)

static void android_os_Parcel_writeString8(JNIEnv* env, jclass clazz, jlong nativePtr, jstring val)

{

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    if (parcel != NULL) {

        status_t err = NO_MEMORY;

        if (val) {

            const size_t len = env->GetStringUTFLength(val);

            const char* str = env->GetStringUTFChars(val, 0);

            if (str) {

                err = parcel->writeString8(str, len);

                env->ReleaseStringUTFChars(val, str);

            }

        } else {

            err = parcel->writeString8(NULL, 0);

        }

        if (err != NO_ERROR) {

            signalExceptionForError(env, clazz, err);

        }

    }

}



static void android_os_Parcel_writeString16(JNIEnv* env, jclass clazz, jlong nativePtr, jstring val)

{

{

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    if (parcel != NULL) {

    if (parcel != NULL) {
@@ -444,7 +465,21 @@ static jdouble android_os_Parcel_readDouble(jlong nativePtr) 
    return 0;

    return 0;

}

}





static jstring android_os_Parcel_readString(JNIEnv* env, jclass clazz, jlong nativePtr)

static jstring android_os_Parcel_readString8(JNIEnv* env, jclass clazz, jlong nativePtr)

{

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    if (parcel != NULL) {

        size_t len;

        const char* str = parcel->readString8Inplace(&len);

        if (str) {

            return env->NewStringUTF(str);

        }

        return NULL;

    }

    return NULL;

}



static jstring android_os_Parcel_readString16(JNIEnv* env, jclass clazz, jlong nativePtr)

{

{

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);

    if (parcel != NULL) {

    if (parcel != NULL) {
@@ -722,7 +757,9 @@ static const JNINativeMethod gParcelMethods[] = { 
    // @FastNative

    // @FastNative

    {"nativeWriteDouble",         "(JD)V", (void*)android_os_Parcel_writeDouble},

    {"nativeWriteDouble",         "(JD)V", (void*)android_os_Parcel_writeDouble},

    // @FastNative

    // @FastNative

    {"nativeWriteString",         "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeString},

    {"nativeWriteString8",        "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeString8},

    // @FastNative

    {"nativeWriteString16",       "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeString16},

    // @FastNative

    // @FastNative

    {"nativeWriteStrongBinder",   "(JLandroid/os/IBinder;)V", (void*)android_os_Parcel_writeStrongBinder},

    {"nativeWriteStrongBinder",   "(JLandroid/os/IBinder;)V", (void*)android_os_Parcel_writeStrongBinder},

    // @FastNative

    // @FastNative
@@ -740,7 +777,9 @@ static const JNINativeMethod gParcelMethods[] = { 
    // @CriticalNative

    // @CriticalNative

    {"nativeReadDouble",          "(J)D", (void*)android_os_Parcel_readDouble},

    {"nativeReadDouble",          "(J)D", (void*)android_os_Parcel_readDouble},

    // @FastNative

    // @FastNative

    {"nativeReadString",          "(J)Ljava/lang/String;", (void*)android_os_Parcel_readString},

    {"nativeReadString8",         "(J)Ljava/lang/String;", (void*)android_os_Parcel_readString8},

    // @FastNative

    {"nativeReadString16",        "(J)Ljava/lang/String;", (void*)android_os_Parcel_readString16},

    // @FastNative

    // @FastNative

    {"nativeReadStrongBinder",    "(J)Landroid/os/IBinder;", (void*)android_os_Parcel_readStrongBinder},

    {"nativeReadStrongBinder",    "(J)Landroid/os/IBinder;", (void*)android_os_Parcel_readStrongBinder},

    // @FastNative

    // @FastNative

core/tests/benchmarks/src/android/os/ParcelStringBenchmark.java

0 → 100644
+72 −0
Original line number Original line Diff line number Diff line 
/*

 * Copyright (C) 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



package android.os;



import com.google.caliper.AfterExperiment;

import com.google.caliper.BeforeExperiment;

import com.google.caliper.Param;



public class ParcelStringBenchmark {



    @Param({"com.example.typical_package_name", "從不喜歡孤單一個 - 蘇永康／吳雨霏"})

    String mValue;



    private Parcel mParcel;



    @BeforeExperiment

    protected void setUp() {

        mParcel = Parcel.obtain();

    }



    @AfterExperiment

    protected void tearDown() {

        mParcel.recycle();

        mParcel = null;

    }



    public void timeWriteString8(int reps) {

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

            mParcel.setDataPosition(0);

            mParcel.writeString8(mValue);

        }

    }



    public void timeReadString8(int reps) {

        mParcel.writeString8(mValue);



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

            mParcel.setDataPosition(0);

            mParcel.readString8();

        }

    }



    public void timeWriteString16(int reps) {

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

            mParcel.setDataPosition(0);

            mParcel.writeString16(mValue);

        }

    }



    public void timeReadString16(int reps) {

        mParcel.writeString16(mValue);



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

            mParcel.setDataPosition(0);

            mParcel.readString16();

        }

    }

}

core/tests/coretests/src/android/os/ParcelTest.java

+23 −0
Original line number Original line Diff line number Diff line
@@ -87,4 +87,27 @@ public class ParcelTest { 




        p.recycle();

        p.recycle();

    }

    }



    /**

     * Verify that writing/reading UTF-8 and UTF-16 strings works well.

     */

    @Test

    public void testStrings() {

        final String[] strings = {

                null, "", "abc\0def", "com.example.typical_package_name",

                "從不喜歡孤單一個 - 蘇永康／吳雨霏", "example"

        };



        final Parcel p = Parcel.obtain();

        for (String string : strings) {

            p.writeString8(string);

            p.writeString16(string);

        }



        p.setDataPosition(0);

        for (String string : strings) {

            assertEquals(string, p.readString8());

            assertEquals(string, p.readString16());

        }

    }

}
 
}