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Commit a2934d5f authored by Jeff Sharkey's avatar Jeff Sharkey
Browse files

Cache AndroidBlockGuardPolicy to avoid allocation. 

Every incoming Binder call ends up triggering a BlockGuardPolicy
update, which would thrash between new AndroidBlockGuardPolicy
instances and BlockGuard.LAX_POLICY, causing GC churn.

This change avoids the extra allocations by recycling a single
AndroidBlockGuardPolicy in a ThreadLocal.  Worst-case thrashing case
is now 10% faster; from 7.46us to 6.65us.

Bug: 9424568
Change-Id: I9c3b1c097a2aecc9b1f109a824cf3ea319fb3393
parent b28f8c82

core/java/android/os/StrictMode.java

+15 −5
Original line number Diff line number Diff line
@@ -783,13 +783,15 @@ public final class StrictMode { 
            BlockGuard.setThreadPolicy(BlockGuard.LAX_POLICY);

            return;

        }

        BlockGuard.Policy policy = BlockGuard.getThreadPolicy();

        if (!(policy instanceof AndroidBlockGuardPolicy)) {

            BlockGuard.setThreadPolicy(new AndroidBlockGuardPolicy(policyMask));

        final BlockGuard.Policy policy = BlockGuard.getThreadPolicy();

        final AndroidBlockGuardPolicy androidPolicy;

        if (policy instanceof AndroidBlockGuardPolicy) {

            androidPolicy = (AndroidBlockGuardPolicy) policy;

        } else {

            AndroidBlockGuardPolicy androidPolicy = (AndroidBlockGuardPolicy) policy;

            androidPolicy.setPolicyMask(policyMask);

            androidPolicy = threadAndroidPolicy.get();

            BlockGuard.setThreadPolicy(androidPolicy);

        }

        androidPolicy.setPolicyMask(policyMask);

    }



    // Sets up CloseGuard in Dalvik/libcore
@@ -1060,6 +1062,14 @@ public final class StrictMode { 
        }

    };



    private static final ThreadLocal<AndroidBlockGuardPolicy>

            threadAndroidPolicy = new ThreadLocal<AndroidBlockGuardPolicy>() {

        @Override

        protected AndroidBlockGuardPolicy initialValue() {

            return new AndroidBlockGuardPolicy(0);

        }

    };



    private static boolean tooManyViolationsThisLoop() {

        return violationsBeingTimed.get().size() >= MAX_OFFENSES_PER_LOOP;

    }

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

0 → 100644
+34 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2013 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 android.os.StrictMode.ThreadPolicy;



import com.google.caliper.SimpleBenchmark;



public class StrictModeBenchmark extends SimpleBenchmark {



    private ThreadPolicy mOff = new ThreadPolicy.Builder().build();

    private ThreadPolicy mOn = new ThreadPolicy.Builder().detectAll().build();



    public void timeToggleThreadPolicy(int reps) {

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

            StrictMode.setThreadPolicy(mOn);

            StrictMode.setThreadPolicy(mOff);

        }

    }

}