Reduce the overhead of find the current snapshot
Now uses a custom implementaiton of a thread local variable
to reduce the overhead of access the current snapshot of a
thread.
Fixes: b/182168191
Test: ./gradlew :compose:r:r:tDUT
Relnote: N/A
Change-Id: Iab53ce4ae2c4396e63581f36014c3318036368e0
diff --git a/compose/runtime/runtime/api/1.0.0-beta02.txt b/compose/runtime/runtime/api/1.0.0-beta02.txt
index a1c11df..d73a573 100644
--- a/compose/runtime/runtime/api/1.0.0-beta02.txt
+++ b/compose/runtime/runtime/api/1.0.0-beta02.txt
@@ -456,6 +456,9 @@
method public static boolean isLiveLiteralsEnabled();
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/api/current.txt b/compose/runtime/runtime/api/current.txt
index a1c11df..d73a573 100644
--- a/compose/runtime/runtime/api/current.txt
+++ b/compose/runtime/runtime/api/current.txt
@@ -456,6 +456,9 @@
method public static boolean isLiveLiteralsEnabled();
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/api/public_plus_experimental_1.0.0-beta02.txt b/compose/runtime/runtime/api/public_plus_experimental_1.0.0-beta02.txt
index f900999d..c803652 100644
--- a/compose/runtime/runtime/api/public_plus_experimental_1.0.0-beta02.txt
+++ b/compose/runtime/runtime/api/public_plus_experimental_1.0.0-beta02.txt
@@ -544,6 +544,9 @@
property public abstract int parameters;
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/api/public_plus_experimental_current.txt b/compose/runtime/runtime/api/public_plus_experimental_current.txt
index f900999d..c803652 100644
--- a/compose/runtime/runtime/api/public_plus_experimental_current.txt
+++ b/compose/runtime/runtime/api/public_plus_experimental_current.txt
@@ -544,6 +544,9 @@
property public abstract int parameters;
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/api/restricted_1.0.0-beta02.txt b/compose/runtime/runtime/api/restricted_1.0.0-beta02.txt
index a334aa4..d80e38d 100644
--- a/compose/runtime/runtime/api/restricted_1.0.0-beta02.txt
+++ b/compose/runtime/runtime/api/restricted_1.0.0-beta02.txt
@@ -483,6 +483,9 @@
method public static boolean isLiveLiteralsEnabled();
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/api/restricted_current.txt b/compose/runtime/runtime/api/restricted_current.txt
index a334aa4..d80e38d 100644
--- a/compose/runtime/runtime/api/restricted_current.txt
+++ b/compose/runtime/runtime/api/restricted_current.txt
@@ -483,6 +483,9 @@
method public static boolean isLiveLiteralsEnabled();
}
+ public final class ThreadMapKt {
+ }
+
}
package androidx.compose.runtime.snapshots {
diff --git a/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Expect.kt b/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Expect.kt
index 2189a52..91193ee 100644
--- a/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Expect.kt
+++ b/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Expect.kt
@@ -26,6 +26,20 @@
internal fun <T> ThreadLocal() = ThreadLocal<T?> { null }
+/**
+ * This is similar to a [ThreadLocal] but has lower overhead because it avoids a weak reference.
+ * This should only be used when the writes are delimited by a try...finally call that will clean
+ * up the reference such as [androidx.compose.runtime.snapshots.Snapshot.enter] else the reference
+ * could get pinned by the thread local causing a leak.
+ *
+ * [ThreadLocal] can be used to implement the actual for platforms that do not exhibit the same
+ * overhead for thread locals as the JVM and ART.
+ */
+internal expect class SnapshotThreadLocal<T>() {
+ fun get(): T?
+ fun set(value: T?)
+}
+
internal expect fun identityHashCode(instance: Any?): Int
@PublishedApi
diff --git a/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/snapshots/Snapshot.kt b/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/snapshots/Snapshot.kt
index 2f73c00..2927d96 100644
--- a/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/snapshots/Snapshot.kt
+++ b/compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/snapshots/Snapshot.kt
@@ -20,7 +20,7 @@
import androidx.compose.runtime.Composable
import androidx.compose.runtime.InternalComposeApi
-import androidx.compose.runtime.ThreadLocal
+import androidx.compose.runtime.SnapshotThreadLocal
import androidx.compose.runtime.synchronized
/**
@@ -1355,7 +1355,10 @@
*/
private const val INVALID_SNAPSHOT = 0
-private val threadSnapshot = ThreadLocal<Snapshot>()
+/**
+ * Current thread snapshot
+ */
+private val threadSnapshot = SnapshotThreadLocal<Snapshot>()
// A global synchronization object. This synchronization object should be taken before modifying any
// of the fields below.
diff --git a/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/ActualJvm.jvm.kt b/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/ActualJvm.jvm.kt
index 7aa0d96..63dbcb1 100644
--- a/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/ActualJvm.jvm.kt
+++ b/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/ActualJvm.jvm.kt
@@ -16,6 +16,9 @@
package androidx.compose.runtime
+import androidx.compose.runtime.internal.ThreadMap
+import androidx.compose.runtime.internal.emptyThreadMap
+
internal actual typealias AtomicReference<V> = java.util.concurrent.atomic.AtomicReference<V>
internal actual open class ThreadLocal<T> actual constructor(
@@ -35,6 +38,23 @@
}
}
+internal actual class SnapshotThreadLocal<T> {
+ private val map = AtomicReference<ThreadMap>(emptyThreadMap)
+ private val writeMutex = Any()
+
+ @Suppress("UNCHECKED_CAST")
+ actual fun get(): T? = map.get().get(Thread.currentThread().id) as T?
+
+ actual fun set(value: T?) {
+ val key = Thread.currentThread().id
+ synchronized(writeMutex) {
+ val current = map.get()
+ if (current.trySet(key, value)) return
+ map.set(current.newWith(key, value))
+ }
+ }
+}
+
internal actual fun identityHashCode(instance: Any?): Int = System.identityHashCode(instance)
@PublishedApi
diff --git a/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/internal/ThreadMap.kt b/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/internal/ThreadMap.kt
new file mode 100644
index 0000000..d4645eb
--- /dev/null
+++ b/compose/runtime/runtime/src/jvmMain/kotlin/androidx/compose/runtime/internal/ThreadMap.kt
@@ -0,0 +1,111 @@
+/*
+ * Copyright 2021 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 androidx.compose.runtime.internal
+
+internal class ThreadMap(
+ private val size: Int,
+ private val keys: LongArray,
+ private val values: Array<Any?>
+) {
+ fun get(key: Long): Any? {
+ val index = find(key)
+ return if (index >= 0) values[index] else null
+ }
+
+ /**
+ * Set the value if it is already in the map. Otherwise a new map must be allocated to contain
+ * the new entry.
+ */
+ fun trySet(key: Long, value: Any?): Boolean {
+ val index = find(key)
+ if (index < 0) return false
+ values[index] = value
+ return true
+ }
+
+ fun newWith(key: Long, value: Any?): ThreadMap {
+ val size = size
+ val newSize = values.count { it != null } + 1
+ val newKeys = LongArray(newSize)
+ val newValues = arrayOfNulls<Any?>(newSize)
+ if (newSize > 1) {
+ var dest = 0
+ var source = 0
+ while (dest < newSize && source < size) {
+ val oldKey = keys[source]
+ val oldValue = values[source]
+ if (oldKey > key) {
+ newKeys[dest] = key
+ newValues[dest] = value
+ dest++
+ // Continue with a loop without this check
+ break
+ }
+ if (oldValue != null) {
+ newKeys[dest] = oldKey
+ newValues[dest] = oldValue
+ dest++
+ }
+ source++
+ }
+ if (source == size) {
+ // Appending a value to the end.
+ newKeys[newSize - 1] = key
+ newValues[newSize - 1] = value
+ } else {
+ while (dest < newSize) {
+ val oldKey = keys[source]
+ val oldValue = values[source]
+ if (oldValue != null) {
+ newKeys[dest] = oldKey
+ newValues[dest] = oldValue
+ dest++
+ }
+ source++
+ }
+ }
+ } else {
+ // The only element
+ newKeys[0] = key
+ newValues[0] = value
+ }
+ return ThreadMap(newSize, newKeys, newValues)
+ }
+
+ private fun find(key: Long): Int {
+ var high = size - 1
+ when (high) {
+ -1 -> return -1
+ 0 -> return if (keys[0] == key) 0 else if (keys[0] > key) -2 else -1
+ }
+ var low = 0
+
+ while (low <= high) {
+ val mid = (low + high).ushr(1)
+ val midVal = keys[mid]
+ val comparison = midVal - key
+ when {
+ comparison < 0 -> low = mid + 1
+ comparison > 0 -> high = mid - 1
+ else -> return mid
+ }
+ }
+ return -(low + 1)
+ }
+}
+
+internal val emptyThreadMap = ThreadMap(0, LongArray(0), emptyArray())
\ No newline at end of file
diff --git a/compose/runtime/runtime/src/test/kotlin/androidx/compose/runtime/snapshots/SnapshotThreadMapTests.kt b/compose/runtime/runtime/src/test/kotlin/androidx/compose/runtime/snapshots/SnapshotThreadMapTests.kt
new file mode 100644
index 0000000..a50c9a8
--- /dev/null
+++ b/compose/runtime/runtime/src/test/kotlin/androidx/compose/runtime/snapshots/SnapshotThreadMapTests.kt
@@ -0,0 +1,162 @@
+/*
+ * Copyright 2021 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 androidx.compose.runtime.snapshots
+
+import androidx.compose.runtime.SnapshotThreadLocal
+import androidx.compose.runtime.internal.ThreadMap
+import kotlin.random.Random
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * Test the internal ThreadMap
+ */
+class SnapshotThreadMapTests {
+ @Test
+ fun canCreateAMap() {
+ val map = emptyThreadMap()
+ assertNotNull(map)
+ }
+
+ @Test
+ fun setOfEmptyFails() {
+ val map = emptyThreadMap()
+ val added = map.trySet(1, 1)
+ assertFalse(added)
+ }
+
+ @Test
+ fun canAddOneToEmpty() {
+ val map = emptyThreadMap()
+ val newMap = map.newWith(1, 1)
+ assertNotEquals(map, newMap)
+ assertEquals(1, newMap.get(1))
+ }
+
+ @Test
+ fun canCreateForward() {
+ val map = testMap(0 until 100)
+ assertNotNull(map)
+ for (i in 0 until 100) {
+ assertEquals(i, map.get(i.toLong()))
+ }
+ for (i in -100 until 0) {
+ assertNull(map.get(i.toLong()))
+ }
+ for (i in 100 until 200) {
+ assertNull(map.get(i.toLong()))
+ }
+ }
+
+ @Test
+ fun canCreateBackward() {
+ val map = testMap((0 until 100).reversed())
+ assertNotNull(map)
+ for (i in 0 until 100) {
+ assertEquals(i, map.get(i.toLong()))
+ }
+ for (i in -100 until 0) {
+ assertNull(map.get(i.toLong()))
+ }
+ for (i in 100 until 200) {
+ assertNull(map.get(i.toLong()))
+ }
+ }
+
+ @Test
+ fun canCreateRandom() {
+ val list = Array<Long>(100) { it.toLong() }
+ val rand = Random(1337)
+ list.shuffle(rand)
+ var map = emptyThreadMap()
+ for (item in list) {
+ map = map.newWith(item, item)
+ }
+ for (i in 0 until 100) {
+ assertEquals(i.toLong(), map.get(i.toLong()))
+ }
+ for (i in -100 until 0) {
+ assertNull(map.get(i.toLong()))
+ }
+ for (i in 100 until 200) {
+ assertNull(map.get(i.toLong()))
+ }
+ }
+
+ @Test
+ fun canRemoveOne() {
+ val map = testMap(1..10)
+ val set = map.trySet(5, null)
+ assertTrue(set)
+ for (i in 1..10) {
+ if (i == 5) {
+ assertNull(map.get(i.toLong()))
+ } else {
+ assertEquals(i, map.get(i.toLong()))
+ }
+ }
+ }
+
+ @Test
+ fun canRemoveOneThenAddOne() {
+ val map = testMap(1..10)
+ val set = map.trySet(5, null)
+ assertTrue(set)
+ val newMap = map.newWith(11, 11)
+ assertNull(newMap.get(5))
+ assertEquals(11, newMap.get(11))
+ }
+
+ private fun emptyThreadMap() = ThreadMap(0, LongArray(0), arrayOfNulls(0))
+
+ private fun testMap(intProgression: IntProgression): ThreadMap {
+ var result = emptyThreadMap()
+ for (i in intProgression) {
+ result = result.newWith(i.toLong(), i)
+ }
+ return result
+ }
+}
+
+/**
+ * Test the thread lcoal variable
+ */
+class SnapshotThreadLocalTests {
+ @Test
+ fun canCreate() {
+ val local = SnapshotThreadLocal<Int>()
+ assertNotNull(local)
+ }
+
+ @Test
+ fun initalValueIsNull() {
+ val local = SnapshotThreadLocal<Int>()
+ assertNull(local.get())
+ }
+
+ @Test
+ fun canSetAndGetTheValue() {
+ val local = SnapshotThreadLocal<Int>()
+ local.set(100)
+ assertEquals(100, local.get())
+ }
+}
\ No newline at end of file
