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Remove Unsafe-based implementation from ExecutionListBenchmark. #7612

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merged 1 commit into from
Jan 10, 2025
Merged

Remove Unsafe-based implementation from ExecutionListBenchmark. #7612

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151 changes: 0 additions & 151 deletions android/guava-tests/benchmark/com/google/common/util/concurrent/ExecutionListBenchmark.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,10 +29,6 @@
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.AbstractFutureBenchmarks.OldAbstractFuture;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.CountDownLatch;
Expand All @@ -44,7 +40,6 @@
import java.util.logging.Logger;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;
import sun.misc.Unsafe;

/** Benchmarks for {@link ExecutionList}. */
@VmOptions({"-Xms8g", "-Xmx8g"})
Expand Down Expand Up @@ -85,29 +80,6 @@ public Object getImpl() {
};
}
},
NEW_WITH_CAS {
@Override
ExecutionListWrapper newExecutionList() {
return new ExecutionListWrapper() {
final ExecutionListUsingCompareAndSwap list = new ExecutionListUsingCompareAndSwap();

@Override
public void add(Runnable runnable, Executor executor) {
list.add(runnable, executor);
}

@Override
public void execute() {
list.execute();
}

@Override
public Object getImpl() {
return list;
}
};
}
},
NEW_WITH_QUEUE {
@Override
ExecutionListWrapper newExecutionList() {
Expand Down Expand Up @@ -578,127 +550,4 @@ private static final class RunnableExecutorPair {
}
}
}

// A version of the list that uses compare and swap to manage the stack without locks.
@SuppressWarnings({"SunApi", "removal"}) // b/345822163
private static final class ExecutionListUsingCompareAndSwap {
static final Logger log = Logger.getLogger(ExecutionListUsingCompareAndSwap.class.getName());

private static final Unsafe UNSAFE;
private static final long HEAD_OFFSET;

/**
* A special instance of {@link RunnableExecutorPair} that is used as a sentinel value for the
* bottom of the stack.
*/
private static final RunnableExecutorPair NULL_PAIR = new RunnableExecutorPair(null, null);

static {
try {
UNSAFE = getUnsafe();
HEAD_OFFSET =
UNSAFE.objectFieldOffset(
ExecutionListUsingCompareAndSwap.class.getDeclaredField("head"));
} catch (Exception ex) {
throw new Error(ex);
}
}

/** TODO(lukes): This was copied verbatim from Striped64.java... standardize this? */
private static Unsafe getUnsafe() {
try {
return Unsafe.getUnsafe();
} catch (SecurityException tryReflectionInstead) {
}
try {
return AccessController.doPrivileged(
new PrivilegedExceptionAction<Unsafe>() {
@Override
public Unsafe run() throws Exception {
Class<Unsafe> k = Unsafe.class;
for (Field f : k.getDeclaredFields()) {
f.setAccessible(true);
Object x = f.get(null);
if (k.isInstance(x)) return k.cast(x);
}
throw new NoSuchFieldError("the Unsafe");
}
});
} catch (PrivilegedActionException e) {
throw new RuntimeException("Could not initialize intrinsics", e.getCause());
}
}

private volatile RunnableExecutorPair head = NULL_PAIR;

public void add(Runnable runnable, Executor executor) {
Preconditions.checkNotNull(runnable, "Runnable was null.");
Preconditions.checkNotNull(executor, "Executor was null.");

RunnableExecutorPair newHead = new RunnableExecutorPair(runnable, executor);
RunnableExecutorPair oldHead;
do {
oldHead = head;
if (oldHead == null) {
// If runnables == null then execute() has been called so we should just execute our
// listener immediately.
newHead.execute();
return;
}
// Try to make newHead the new head of the stack at runnables.
newHead.next = oldHead;
} while (!UNSAFE.compareAndSwapObject(this, HEAD_OFFSET, oldHead, newHead));
}

public void execute() {
RunnableExecutorPair stack;
do {
stack = head;
if (stack == null) {
// If head == null then execute() has been called so we should just return
return;
}
// try to swap null into head.
} while (!UNSAFE.compareAndSwapObject(this, HEAD_OFFSET, stack, null));

RunnableExecutorPair reversedStack = null;
while (stack != NULL_PAIR) {
RunnableExecutorPair head = stack;
stack = stack.next;
head.next = reversedStack;
reversedStack = head;
}
stack = reversedStack;
while (stack != null) {
stack.execute();
stack = stack.next;
}
}

private static class RunnableExecutorPair {
final Runnable runnable;
final Executor executor;
// Volatile because this is written on one thread and read on another with no synchronization.
@Nullable volatile RunnableExecutorPair next;

RunnableExecutorPair(@Nullable Runnable runnable, @Nullable Executor executor) {
this.runnable = runnable;
this.executor = executor;
}

void execute() {
try {
executor.execute(runnable);
} catch (RuntimeException e) {
log.log(
Level.SEVERE,
"RuntimeException while executing runnable "
+ runnable
+ " with executor "
+ executor,
e);
}
}
}
}
}
151 changes: 0 additions & 151 deletions guava-tests/benchmark/com/google/common/util/concurrent/ExecutionListBenchmark.java
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,10 +29,6 @@
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.AbstractFutureBenchmarks.OldAbstractFuture;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.CountDownLatch;
Expand All @@ -44,7 +40,6 @@
import java.util.logging.Logger;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;
import sun.misc.Unsafe;

/** Benchmarks for {@link ExecutionList}. */
@VmOptions({"-Xms8g", "-Xmx8g"})
Expand Down Expand Up @@ -85,29 +80,6 @@ public Object getImpl() {
};
}
},
NEW_WITH_CAS {
@Override
ExecutionListWrapper newExecutionList() {
return new ExecutionListWrapper() {
final ExecutionListUsingCompareAndSwap list = new ExecutionListUsingCompareAndSwap();

@Override
public void add(Runnable runnable, Executor executor) {
list.add(runnable, executor);
}

@Override
public void execute() {
list.execute();
}

@Override
public Object getImpl() {
return list;
}
};
}
},
NEW_WITH_QUEUE {
@Override
ExecutionListWrapper newExecutionList() {
Expand Down Expand Up @@ -578,127 +550,4 @@ private static final class RunnableExecutorPair {
}
}
}

// A version of the list that uses compare and swap to manage the stack without locks.
@SuppressWarnings({"SunApi", "removal"}) // b/345822163
private static final class ExecutionListUsingCompareAndSwap {
static final Logger log = Logger.getLogger(ExecutionListUsingCompareAndSwap.class.getName());

private static final Unsafe UNSAFE;
private static final long HEAD_OFFSET;

/**
* A special instance of {@link RunnableExecutorPair} that is used as a sentinel value for the
* bottom of the stack.
*/
private static final RunnableExecutorPair NULL_PAIR = new RunnableExecutorPair(null, null);

static {
try {
UNSAFE = getUnsafe();
HEAD_OFFSET =
UNSAFE.objectFieldOffset(
ExecutionListUsingCompareAndSwap.class.getDeclaredField("head"));
} catch (Exception ex) {
throw new Error(ex);
}
}

/** TODO(lukes): This was copied verbatim from Striped64.java... standardize this? */
private static Unsafe getUnsafe() {
try {
return Unsafe.getUnsafe();
} catch (SecurityException tryReflectionInstead) {
}
try {
return AccessController.doPrivileged(
new PrivilegedExceptionAction<Unsafe>() {
@Override
public Unsafe run() throws Exception {
Class<Unsafe> k = Unsafe.class;
for (Field f : k.getDeclaredFields()) {
f.setAccessible(true);
Object x = f.get(null);
if (k.isInstance(x)) return k.cast(x);
}
throw new NoSuchFieldError("the Unsafe");
}
});
} catch (PrivilegedActionException e) {
throw new RuntimeException("Could not initialize intrinsics", e.getCause());
}
}

private volatile RunnableExecutorPair head = NULL_PAIR;

public void add(Runnable runnable, Executor executor) {
Preconditions.checkNotNull(runnable, "Runnable was null.");
Preconditions.checkNotNull(executor, "Executor was null.");

RunnableExecutorPair newHead = new RunnableExecutorPair(runnable, executor);
RunnableExecutorPair oldHead;
do {
oldHead = head;
if (oldHead == null) {
// If runnables == null then execute() has been called so we should just execute our
// listener immediately.
newHead.execute();
return;
}
// Try to make newHead the new head of the stack at runnables.
newHead.next = oldHead;
} while (!UNSAFE.compareAndSwapObject(this, HEAD_OFFSET, oldHead, newHead));
}

public void execute() {
RunnableExecutorPair stack;
do {
stack = head;
if (stack == null) {
// If head == null then execute() has been called so we should just return
return;
}
// try to swap null into head.
} while (!UNSAFE.compareAndSwapObject(this, HEAD_OFFSET, stack, null));

RunnableExecutorPair reversedStack = null;
while (stack != NULL_PAIR) {
RunnableExecutorPair head = stack;
stack = stack.next;
head.next = reversedStack;
reversedStack = head;
}
stack = reversedStack;
while (stack != null) {
stack.execute();
stack = stack.next;
}
}

private static class RunnableExecutorPair {
final Runnable runnable;
final Executor executor;
// Volatile because this is written on one thread and read on another with no synchronization.
@Nullable volatile RunnableExecutorPair next;

RunnableExecutorPair(@Nullable Runnable runnable, @Nullable Executor executor) {
this.runnable = runnable;
this.executor = executor;
}

void execute() {
try {
executor.execute(runnable);
} catch (RuntimeException e) {
log.log(
Level.SEVERE,
"RuntimeException while executing runnable "
+ runnable
+ " with executor "
+ executor,
e);
}
}
}
}
}
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