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Simplify InternalThreadLocalMap (#10872)

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Motivation:
I did not see any tangible advantage to the padding.
The only other field that was guarded was a rarely changed object reference to a BitSet.
Without the padding, there is also no longer any use of the inheritance hierarchy.
The padding was also using `long`, which would not necessarily prevent the JVM from fitting the aforementioned object reference in an alignment gap.

Modification:
Move all the fields into the InternalThreadLocalMap and deprecate the stuff we'd like to remove.

Result:
Simpler code.
This resolves the discussion in https://github.com/netty/netty/issues/9284
This commit is contained in:
Chris Vest 2020-12-18 08:06:53 +01:00 committed by GitHub
parent a9ec3d86f6
commit 5c1613df81
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 30 additions and 46 deletions
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34
common/src/main/java/io/netty/util/internal/InternalThreadLocalMap.java
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@ -30,6 +30,7 @@ import java.util.BitSet;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
* The internal data structure that stores the thread-local variables for Netty and all {@link FastThreadLocal}s.
@ -39,6 +40,9 @@ import java.util.WeakHashMap;
public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(InternalThreadLocalMap.class);
private static final ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap =
new ThreadLocal<InternalThreadLocalMap>();
private static final AtomicInteger nextIndex = new AtomicInteger();
private static final int DEFAULT_ARRAY_LIST_INITIAL_CAPACITY = 8;
private static final int STRING_BUILDER_INITIAL_SIZE;
@ -48,8 +52,31 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
public static final Object UNSET = new Object();
/** Used by {@link FastThreadLocal} */
private Object[] indexedVariables;
// Core thread-locals
private int futureListenerStackDepth;
private int localChannelReaderStackDepth;
private Map<Class<?>, Boolean> handlerSharableCache;
private IntegerHolder counterHashCode;
private ThreadLocalRandom random;
private Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache;
private Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache;
// String-related thread-locals
private StringBuilder stringBuilder;
private Map<Charset, CharsetEncoder> charsetEncoderCache;
private Map<Charset, CharsetDecoder> charsetDecoderCache;
// ArrayList-related thread-locals
private ArrayList<Object> arrayList;
private BitSet cleanerFlags;
/** @deprecated These padding fields will be removed in the future. */
public long rp1, rp2, rp3, rp4, rp5, rp6, rp7, rp8, rp9;
static {
STRING_BUILDER_INITIAL_SIZE =
SystemPropertyUtil.getInt("io.netty.threadLocalMap.stringBuilder.initialSize", 1024);
@ -85,7 +112,6 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
}
private static InternalThreadLocalMap slowGet() {
ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = UnpaddedInternalThreadLocalMap.slowThreadLocalMap;
InternalThreadLocalMap ret = slowThreadLocalMap.get();
if (ret == null) {
ret = new InternalThreadLocalMap();
@ -120,12 +146,8 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
return nextIndex.get() - 1;
}
// Cache line padding (must be public)
// With CompressedOops enabled, an instance of this class should occupy at least 128 bytes.
public long rp1, rp2, rp3, rp4, rp5, rp6, rp7, rp8, rp9;
private InternalThreadLocalMap() {
super(newIndexedVariableTable());
indexedVariables = newIndexedVariableTable();
}
private static Object[] newIndexedVariableTable() {

42
common/src/main/java/io/netty/util/internal/UnpaddedInternalThreadLocalMap.java
View File

@ -13,49 +13,11 @@
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.util.internal;
import io.netty.util.concurrent.FastThreadLocal;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.util.ArrayList;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
/**
* The internal data structure that stores the thread-local variables for Netty and all {@link FastThreadLocal}s.
* Note that this class is for internal use only and is subject to change at any time. Use {@link FastThreadLocal}
* unless you know what you are doing.
* @deprecated This class will be removed in the future.
*/
class UnpaddedInternalThreadLocalMap {
static final ThreadLocal<InternalThreadLocalMap> slowThreadLocalMap = new ThreadLocal<InternalThreadLocalMap>();
static final AtomicInteger nextIndex = new AtomicInteger();
/** Used by {@link FastThreadLocal} */
Object[] indexedVariables;
// Core thread-locals
int futureListenerStackDepth;
int localChannelReaderStackDepth;
Map<Class<?>, Boolean> handlerSharableCache;
IntegerHolder counterHashCode;
ThreadLocalRandom random;
Map<Class<?>, TypeParameterMatcher> typeParameterMatcherGetCache;
Map<Class<?>, Map<String, TypeParameterMatcher>> typeParameterMatcherFindCache;
// String-related thread-locals
StringBuilder stringBuilder;
Map<Charset, CharsetEncoder> charsetEncoderCache;
Map<Charset, CharsetDecoder> charsetDecoderCache;
// ArrayList-related thread-locals
ArrayList<Object> arrayList;
UnpaddedInternalThreadLocalMap(Object[] indexedVariables) {
this.indexedVariables = indexedVariables;
}
// We cannot remove this in 4.1 because it could break compatibility.
}