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Commit c64df8c3 authored by Shai Barack's avatar Shai Barack
Browse files

Add StringCache, and use it when unparceling Strings 

StringCache is like String.intern() but weaker.
The goal is to dedupe runtime string allocations, starting with parceled strings.

This use case was driven by field stats for String allocations, many of which come from incoming parcels.

Results from running this on a local test device:
https://docs.google.com/spreadsheets/d/1HlLZTX88SPHHpjdKkDGI2wvS-vLhBLeSy6EfR9tXMXE/edit?usp=sharing&resourcekey=0-uNRHRp80IMmVqE0Oe1p7og

Most processes are showing >80% hit rate.

After this is merged, I will study the impact in trunk partial on heap size, post-GC metrics, and other memory KPIs.

Flag: android.os.parcel_string_cache_enabled
Bug: 442140362
Test: StringCacheTest

Change-Id: I07912887d4564bc8cd3251b13d7102ff287a34df
parent 979f61ae

boot/boot-image-profile-extra.txt

+3 −0
Original line number Diff line number Diff line
@@ -94,3 +94,6 @@ Lcom/android/internal/pm/SystemFeaturesMetadata; 
# TOOD(b/417492941): Remove after inclusion in generated boot-image-profile.txt.

HSPLandroid/os/Process;->setThreadPriority(II)V

HSPLandroid/os/Process;->setThreadPriority(I)V



# TODO: remove after the generated profile is updated.

HSPLcom/android/internal/util/StringCache;->*

boot/preloaded-classes

+1 −0
Original line number Diff line number Diff line
@@ -13974,6 +13974,7 @@ com.android.internal.util.StateMachine$SmHandler$StateInfo 
com.android.internal.util.StateMachine$SmHandler

com.android.internal.util.StateMachine-IA

com.android.internal.util.StateMachine

com.android.internal.util.StringCache

com.android.internal.util.StringPool

com.android.internal.util.SyncResultReceiver$TimeoutException

com.android.internal.util.SyncResultReceiver

core/java/android/app/ActivityThread.java

+10 −0
Original line number Diff line number Diff line
@@ -255,6 +255,7 @@ import com.android.internal.protolog.ProtoLog; 
import com.android.internal.util.ArrayUtils;

import com.android.internal.util.FastPrintWriter;

import com.android.internal.util.Preconditions;

import com.android.internal.util.StringCache;

import com.android.internal.util.function.pooled.PooledLambda;

import com.android.org.conscrypt.TrustedCertificateStore;

import com.android.server.am.BitmapDumpProto;
@@ -1953,6 +1954,10 @@ public final class ActivityThread extends ClientTransactionHandler 
            }



            pw.println(" ");



            if (android.os.Flags.parcelStringCacheEnabled()) {

                StringCache.INSTANCE.dump(pw);

            }

        }



        @NeverCompile
@@ -7710,6 +7715,11 @@ public final class ActivityThread extends ClientTransactionHandler 
        }



        WindowManagerGlobal.getInstance().trimMemory(level);



        if (android.os.Flags.parcelStringCacheEnabled()

                && level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND) {

            StringCache.INSTANCE.clear();

        }

    }



    private void setupGraphicsSupport(Context context) {

core/java/android/os/Parcel.java

+11 −2
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ import android.util.SparseIntArray; 
import com.android.internal.annotations.GuardedBy;

import com.android.internal.annotations.VisibleForTesting;

import com.android.internal.util.ArrayUtils;

import com.android.internal.util.StringCache;



import dalvik.annotation.optimization.CriticalNative;

import dalvik.annotation.optimization.FastNative;
@@ -3450,13 +3451,21 @@ public final class Parcel { 


    /** @hide */

    public @Nullable String readString8NoHelper() {

        if (Flags.parcelStringCacheEnabled()) {

            return StringCache.INSTANCE.cache(nativeReadString8(mNativePtr));

        } else {

            return nativeReadString8(mNativePtr);

        }

    }



    /** @hide */

    public @Nullable String readString16NoHelper() {

        if (Flags.parcelStringCacheEnabled()) {

            return StringCache.INSTANCE.cache(nativeReadString16(mNativePtr));

        } else {

            return nativeReadString16(mNativePtr);

        }

    }



    /**

     * Read a boolean value from the parcel at the current dataPosition().

core/java/com/android/internal/util/OWNERS

+3 −0
Original line number Diff line number Diff line
@@ -9,3 +9,6 @@ per-file *Screenshot* = file:/packages/SystemUI/src/com/android/systemui/screens 
per-file *LatencyTracker* = file:/core/java/com/android/internal/util/LATENCY_TRACKER_OWNERS

# Haptics

per-file *Vibrat*.java = file:/services/core/java/com/android/server/vibrator/OWNERS



# Performance

per-file StringCache.java = file:/PERFORMANCE_OWNERS