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CompositeByteBuf optimizations and new addFlattenedComponents method (#8939)

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Motivation:

The CompositeByteBuf discardReadBytes / discardReadComponents methods are currently quite inefficient, including when there are no read components to discard. We would like to call the latter more frequently in ByteToMessageDecoder#COMPOSITE_CUMULATOR.

In the same context it would be beneficial to perform a "shallow copy" of a composite buffer (for example when it has a refcount > 1) to avoid having to allocate and copy the contained bytes just to obtain an "independent" cumulation.

Modifications:

- Optimize discardReadBytes() and discardReadComponents() implementations (start at first comp rather than performing a binary search for the readerIndex).
- New addFlattenedComponents(boolean,ByteBuf) method which performs a shallow copy if the provided buffer is also composite and avoids adding any empty buffers, plus unit test.
- Other minor optimizations to avoid unnecessary checks.

Results:

discardReadXX methods are faster, composite buffers can be easily appended without deepening the buffer "tree" or retaining unused components.
This commit is contained in:
Nick Hill 2019-04-08 11:48:08 -07:00 committed by Norman Maurer
parent 4c56e4bad6
commit 1f93bd36b6
4 changed files with 190 additions and 38 deletions
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6
buffer/src/main/java/io/netty/buffer/AdvancedLeakAwareCompositeByteBuf.java
View File

@ -939,6 +939,12 @@ final class AdvancedLeakAwareCompositeByteBuf extends SimpleLeakAwareCompositeBy
return super.addComponent(increaseWriterIndex, cIndex, buffer);
}
@Override
public CompositeByteBuf addFlattenedComponents(boolean increaseWriterIndex, ByteBuf buffer) {
recordLeakNonRefCountingOperation(leak);
return super.addFlattenedComponents(increaseWriterIndex, buffer);
}
@Override
public CompositeByteBuf removeComponent(int cIndex) {
recordLeakNonRefCountingOperation(leak);

151
buffer/src/main/java/io/netty/buffer/CompositeByteBuf.java
View File

@ -287,7 +287,7 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
c.reposition(components[cIndex - 1].endOffset);
}
if (increaseWriterIndex) {
writerIndex(writerIndex() + readableBytes);
writerIndex += readableBytes;
}
return cIndex;
} finally {
@ -370,7 +370,7 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
updateComponentOffsets(ci); // only need to do this here for components after the added ones
}
if (increaseWriterIndex && ci > cIndex && ci <= componentCount) {
writerIndex(writerIndex() + components[ci - 1].endOffset - components[cIndex].offset);
writerIndex += components[ci - 1].endOffset - components[cIndex].offset;
}
}
}
@ -413,6 +413,74 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
return addComponents(false, cIndex, buffers);
}
/**
* Add the given {@link ByteBuf} and increase the {@code writerIndex} if {@code increaseWriterIndex} is
* {@code true}. If the provided buffer is a {@link CompositeByteBuf} itself, a "shallow copy" of its
* readable components will be performed. Thus the actual number of new components added may vary
* and in particular will be zero if the provided buffer is not readable.
* <p>
* {@link ByteBuf#release()} ownership of {@code buffer} is transferred to this {@link CompositeByteBuf}.
* @param buffer the {@link ByteBuf} to add. {@link ByteBuf#release()} ownership is transferred to this
* {@link CompositeByteBuf}.
*/
public CompositeByteBuf addFlattenedComponents(boolean increaseWriterIndex, ByteBuf buffer) {
requireNonNull(buffer, "buffer");
final int ridx = buffer.readerIndex();
final int widx = buffer.writerIndex();
if (ridx == widx) {
buffer.release();
return this;
}
if (!(buffer instanceof CompositeByteBuf)) {
addComponent0(increaseWriterIndex, componentCount, buffer);
consolidateIfNeeded();
return this;
}
final CompositeByteBuf from = (CompositeByteBuf) buffer;
from.checkIndex(ridx, widx - ridx);
final Component[] fromComponents = from.components;
final int compCountBefore = componentCount;
final int writerIndexBefore = writerIndex;
try {
for (int cidx = from.toComponentIndex0(ridx), newOffset = capacity();; cidx++) {
final Component component = fromComponents[cidx];
final int compOffset = component.offset;
final int fromIdx = Math.max(ridx, compOffset);
final int toIdx = Math.min(widx, component.endOffset);
final int len = toIdx - fromIdx;
if (len > 0) { // skip empty components
// Note that it's safe to just retain the unwrapped buf here, even in the case
// of PooledSlicedByteBufs - those slices will still be properly released by the
// source Component's free() method.
addComp(componentCount, new Component(
component.buf.retain(), component.idx(fromIdx), newOffset, len, null));
}
if (widx == toIdx) {
break;
}
newOffset += len;
}
if (increaseWriterIndex) {
writerIndex = writerIndexBefore + (widx - ridx);
}
consolidateIfNeeded();
buffer.release();
buffer = null;
return this;
} finally {
if (buffer != null) {
// if we did not succeed, attempt to rollback any components that were added
if (increaseWriterIndex) {
writerIndex = writerIndexBefore;
}
for (int cidx = componentCount - 1; cidx >= compCountBefore; cidx--) {
components[cidx].free();
removeComp(cidx);
}
}
}
}
// TODO optimize further, similar to ByteBuf[] version
// (difference here is that we don't know *always* know precise size increase in advance,
// but we do in the most common case that the Iterable is a Collection)
@ -766,9 +834,9 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
removeCompRange(i + 1, size);
if (readerIndex() > newCapacity) {
setIndex(newCapacity, newCapacity);
} else if (writerIndex() > newCapacity) {
writerIndex(newCapacity);
setIndex0(newCapacity, newCapacity);
} else if (writerIndex > newCapacity) {
writerIndex = newCapacity;
}
}
return this;
@ -815,6 +883,9 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
}
}
}
if (size <= 2) { // fast-path for 1 and 2 component count
return size == 1 || offset < components[0].endOffset ? 0 : 1;
}
for (int low = 0, high = size; low <= high;) {
int mid = low + high >>> 1;
Component c = components[mid];
@ -1678,16 +1749,26 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
}
// Remove read components.
int firstComponentId = toComponentIndex0(readerIndex);
for (int i = 0; i < firstComponentId; i ++) {
components[i].free();
int firstComponentId = 0;
Component c = null;
for (int size = componentCount; firstComponentId < size; firstComponentId++) {
c = components[firstComponentId];
if (c.endOffset > readerIndex) {
break;
}
c.free();
}
if (firstComponentId == 0) {
return this; // Nothing to discard
}
Component la = lastAccessed;
if (la != null && la.endOffset < readerIndex) {
lastAccessed = null;
}
lastAccessed = null;
removeCompRange(0, firstComponentId);
// Update indexes and markers.
Component first = components[0];
int offset = first.offset;
int offset = c.offset;
updateComponentOffsets(0);
setIndex(readerIndex - offset, writerIndex - offset);
return this;
@ -1713,36 +1794,30 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf implements
return this;
}
// Remove read components.
int firstComponentId = toComponentIndex0(readerIndex);
for (int i = 0; i < firstComponentId; i ++) {
Component c = components[i];
c.free();
if (lastAccessed == c) {
lastAccessed = null;
int firstComponentId = 0;
Component c = null;
for (int size = componentCount; firstComponentId < size; firstComponentId++) {
c = components[firstComponentId];
if (c.endOffset > readerIndex) {
break;
}
c.free();
}
// Remove or replace the first readable component with a new slice.
Component c = components[firstComponentId];
if (readerIndex == c.endOffset) {
// new slice would be empty, so remove instead
c.free();
if (lastAccessed == c) {
lastAccessed = null;
}
firstComponentId++;
} else {
int trimmedBytes = readerIndex - c.offset;
c.offset = 0;
c.endOffset -= readerIndex;
c.adjustment += readerIndex;
ByteBuf slice = c.slice;
if (slice != null) {
// We must replace the cached slice with a derived one to ensure that
// it can later be released properly in the case of PooledSlicedByteBuf.
c.slice = slice.slice(trimmedBytes, c.length());
}
// Replace the first readable component with a new slice.
int trimmedBytes = readerIndex - c.offset;
c.offset = 0;
c.endOffset -= readerIndex;
c.adjustment += readerIndex;
ByteBuf slice = c.slice;
if (slice != null) {
// We must replace the cached slice with a derived one to ensure that
// it can later be released properly in the case of PooledSlicedByteBuf.
c.slice = slice.slice(trimmedBytes, c.length());
}
Component la = lastAccessed;
if (la != null && la.endOffset < readerIndex) {
lastAccessed = null;
}
removeCompRange(0, firstComponentId);

6
buffer/src/main/java/io/netty/buffer/WrappedCompositeByteBuf.java
View File

@ -548,6 +548,12 @@ class WrappedCompositeByteBuf extends CompositeByteBuf {
return this;
}
@Override
public CompositeByteBuf addFlattenedComponents(boolean increaseWriterIndex, ByteBuf buffer) {
wrapped.addFlattenedComponents(increaseWriterIndex, buffer);
return this;
}
@Override
public CompositeByteBuf removeComponent(int cIndex) {
wrapped.removeComponent(cIndex);

65
buffer/src/test/java/io/netty/buffer/AbstractCompositeByteBufTest.java
View File

@ -1086,6 +1086,71 @@ public abstract class AbstractCompositeByteBufTest extends AbstractByteBufTest {
cbuf.release();
}
@Test
public void testAddFlattenedComponents() {
ByteBuf b1 = Unpooled.wrappedBuffer(new byte[] { 1, 2, 3 });
CompositeByteBuf newComposite = Unpooled.compositeBuffer()
.addComponent(true, b1)
.addFlattenedComponents(true, b1.retain())
.addFlattenedComponents(true, Unpooled.EMPTY_BUFFER);
assertEquals(2, newComposite.numComponents());
assertEquals(6, newComposite.capacity());
assertEquals(6, newComposite.writerIndex());
// It is important to use a pooled allocator here to ensure
// the slices returned by readRetainedSlice are of type
// PooledSlicedByteBuf, which maintains an independent refcount
// (so that we can be sure to cover this case)
ByteBuf buffer = PooledByteBufAllocator.DEFAULT.buffer()
.writeBytes(new byte[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10});
// use mixture of slice and retained slice
ByteBuf s1 = buffer.readRetainedSlice(2);
ByteBuf s2 = s1.retainedSlice(0, 2);
ByteBuf s3 = buffer.slice(0, 2).retain();
ByteBuf s4 = s2.retainedSlice(0, 2);
buffer.release();
ByteBuf compositeToAdd = Unpooled.compositeBuffer()
.addComponent(s1)
.addComponent(Unpooled.EMPTY_BUFFER)
.addComponents(s2, s3, s4);
// set readable range to be from middle of first component
// to middle of penultimate component
compositeToAdd.setIndex(1, 5);
assertEquals(1, compositeToAdd.refCnt());
assertEquals(1, s4.refCnt());
ByteBuf compositeCopy = compositeToAdd.copy();
newComposite.addFlattenedComponents(true, compositeToAdd);
// verify that added range matches
ByteBufUtil.equals(compositeCopy, 0,
newComposite, 6, compositeCopy.readableBytes());
// should not include empty component or last component
// (latter outside of the readable range)
assertEquals(5, newComposite.numComponents());
assertEquals(10, newComposite.capacity());
assertEquals(10, newComposite.writerIndex());
assertEquals(0, compositeToAdd.refCnt());
// s4 wasn't in added range so should have been jettisoned
assertEquals(0, s4.refCnt());
assertEquals(1, newComposite.refCnt());
// releasing composite should release the remaining components
newComposite.release();
assertEquals(0, newComposite.refCnt());
assertEquals(0, s1.refCnt());
assertEquals(0, s2.refCnt());
assertEquals(0, s3.refCnt());
assertEquals(0, b1.refCnt());
}
@Test
public void testIterator() {
CompositeByteBuf cbuf = compositeBuffer();