Respect ChannelConfig.getWriteSpinCount() when using epoll transport
Motivation: The writeSpinCount was ignored in the epoll transport and it just kept on trying writing. This could cause unnessary cpu spinning if a slow remote peer was reading the data very very slow. Modification: - Correctly take writeSpinCount into account when writing. Result: Less cpu spinning when writing to a slow remote peer.
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@ -235,14 +235,14 @@ abstract class AbstractEpollChannel extends AbstractChannel {
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return localReadAmount;
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}
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protected final int doWriteBytes(ByteBuf buf) throws Exception {
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protected final int doWriteBytes(ByteBuf buf, int writeSpinCount) throws Exception {
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int readableBytes = buf.readableBytes();
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int writtenBytes = 0;
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if (buf.hasMemoryAddress()) {
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long memoryAddress = buf.memoryAddress();
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int readerIndex = buf.readerIndex();
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int writerIndex = buf.writerIndex();
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for (;;) {
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for (int i = writeSpinCount - 1; i >= 0; i--) {
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int localFlushedAmount = Native.writeAddress(
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fileDescriptor.intValue(), memoryAddress, readerIndex, writerIndex);
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if (localFlushedAmount > 0) {
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@ -252,9 +252,7 @@ abstract class AbstractEpollChannel extends AbstractChannel {
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}
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readerIndex += localFlushedAmount;
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} else {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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return writtenBytes;
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break;
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}
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}
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} else {
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@ -264,7 +262,7 @@ abstract class AbstractEpollChannel extends AbstractChannel {
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} else {
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nioBuf = buf.nioBuffer();
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}
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for (;;) {
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for (int i = writeSpinCount - 1; i >= 0; i--) {
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int pos = nioBuf.position();
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int limit = nioBuf.limit();
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int localFlushedAmount = Native.write(fileDescriptor.intValue(), nioBuf, pos, limit);
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@ -275,13 +273,15 @@ abstract class AbstractEpollChannel extends AbstractChannel {
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return writtenBytes;
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}
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} else {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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break;
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}
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}
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return writtenBytes;
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}
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if (writtenBytes < readableBytes) {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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}
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return writtenBytes;
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}
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protected abstract class AbstractEpollUnsafe extends AbstractUnsafe {
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@ -70,7 +70,7 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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* Write bytes form the given {@link ByteBuf} to the underlying {@link java.nio.channels.Channel}.
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* @param buf the {@link ByteBuf} from which the bytes should be written
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*/
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private boolean writeBytes(ChannelOutboundBuffer in, ByteBuf buf) throws Exception {
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private boolean writeBytes(ChannelOutboundBuffer in, ByteBuf buf, int writeSpinCount) throws Exception {
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int readableBytes = buf.readableBytes();
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if (readableBytes == 0) {
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in.remove();
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@ -78,16 +78,17 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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}
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if (buf.hasMemoryAddress() || buf.nioBufferCount() == 1) {
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int writtenBytes = doWriteBytes(buf);
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int writtenBytes = doWriteBytes(buf, writeSpinCount);
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in.removeBytes(writtenBytes);
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return writtenBytes == readableBytes;
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} else {
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ByteBuffer[] nioBuffers = buf.nioBuffers();
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return writeBytesMultiple(in, nioBuffers, nioBuffers.length, readableBytes);
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return writeBytesMultiple(in, nioBuffers, nioBuffers.length, readableBytes, writeSpinCount);
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}
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}
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private boolean writeBytesMultiple(ChannelOutboundBuffer in, IovArray array) throws IOException {
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private boolean writeBytesMultiple(
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ChannelOutboundBuffer in, IovArray array, int writeSpinCount) throws IOException {
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long expectedWrittenBytes = array.size();
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final long initialExpectedWrittenBytes = expectedWrittenBytes;
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@ -100,11 +101,9 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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boolean done = false;
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int offset = 0;
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int end = offset + cnt;
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for (;;) {
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for (int i = writeSpinCount - 1; i >= 0; i--) {
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long localWrittenBytes = Native.writevAddresses(fd().intValue(), array.memoryAddress(offset), cnt);
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if (localWrittenBytes == 0) {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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break;
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}
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expectedWrittenBytes -= localWrittenBytes;
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@ -127,14 +126,16 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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}
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} while (offset < end && localWrittenBytes > 0);
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}
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if (!done) {
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setFlag(Native.EPOLLOUT);
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}
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in.removeBytes(initialExpectedWrittenBytes - expectedWrittenBytes);
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return done;
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}
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private boolean writeBytesMultiple(
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ChannelOutboundBuffer in, ByteBuffer[] nioBuffers,
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int nioBufferCnt, long expectedWrittenBytes) throws IOException {
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int nioBufferCnt, long expectedWrittenBytes, int writeSpinCount) throws IOException {
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assert expectedWrittenBytes != 0;
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final long initialExpectedWrittenBytes = expectedWrittenBytes;
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@ -142,11 +143,9 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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boolean done = false;
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int offset = 0;
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int end = offset + nioBufferCnt;
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for (;;) {
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for (int i = writeSpinCount - 1; i >= 0; i--) {
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long localWrittenBytes = Native.writev(fd().intValue(), nioBuffers, offset, nioBufferCnt);
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if (localWrittenBytes == 0) {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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break;
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}
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expectedWrittenBytes -= localWrittenBytes;
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@ -173,6 +172,9 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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}
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in.removeBytes(initialExpectedWrittenBytes - expectedWrittenBytes);
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if (!done) {
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setFlag(Native.EPOLLOUT);
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}
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return done;
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}
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@ -182,7 +184,8 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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* @param region the {@link DefaultFileRegion} from which the bytes should be written
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* @return amount the amount of written bytes
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*/
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private boolean writeFileRegion(ChannelOutboundBuffer in, DefaultFileRegion region) throws Exception {
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private boolean writeFileRegion(
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ChannelOutboundBuffer in, DefaultFileRegion region, int writeSpinCount) throws Exception {
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final long regionCount = region.count();
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if (region.transfered() >= regionCount) {
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in.remove();
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@ -193,13 +196,11 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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boolean done = false;
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long flushedAmount = 0;
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for (;;) {
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for (int i = writeSpinCount - 1; i >= 0; i--) {
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final long offset = region.transfered();
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final long localFlushedAmount =
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Native.sendfile(fd().intValue(), region, baseOffset, offset, regionCount - offset);
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if (localFlushedAmount == 0) {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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break;
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}
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@ -216,12 +217,16 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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if (done) {
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in.remove();
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} else {
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// Returned EAGAIN need to set EPOLLOUT
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setFlag(Native.EPOLLOUT);
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}
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return done;
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}
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@Override
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protected void doWrite(ChannelOutboundBuffer in) throws Exception {
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int writeSpinCount = config().getWriteSpinCount();
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for (;;) {
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final int msgCount = in.size();
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@ -233,7 +238,7 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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// Do gathering write if the outbounf buffer entries start with more than one ByteBuf.
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if (msgCount > 1 && in.current() instanceof ByteBuf) {
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if (!doWriteMultiple(in)) {
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if (!doWriteMultiple(in, writeSpinCount)) {
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break;
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}
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@ -241,26 +246,26 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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// because a user might have triggered another write and flush when we notify his or her
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// listeners.
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} else { // msgCount == 1
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if (!doWriteSingle(in)) {
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if (!doWriteSingle(in, writeSpinCount)) {
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break;
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}
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}
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}
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}
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protected boolean doWriteSingle(ChannelOutboundBuffer in) throws Exception {
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protected boolean doWriteSingle(ChannelOutboundBuffer in, int writeSpinCount) throws Exception {
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// The outbound buffer contains only one message or it contains a file region.
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Object msg = in.current();
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if (msg instanceof ByteBuf) {
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ByteBuf buf = (ByteBuf) msg;
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if (!writeBytes(in, buf)) {
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if (!writeBytes(in, buf, writeSpinCount)) {
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// was not able to write everything so break here we will get notified later again once
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// the network stack can handle more writes.
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return false;
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}
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} else if (msg instanceof DefaultFileRegion) {
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DefaultFileRegion region = (DefaultFileRegion) msg;
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if (!writeFileRegion(in, region)) {
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if (!writeFileRegion(in, region, writeSpinCount)) {
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// was not able to write everything so break here we will get notified later again once
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// the network stack can handle more writes.
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return false;
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@ -273,14 +278,14 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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return true;
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}
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private boolean doWriteMultiple(ChannelOutboundBuffer in) throws Exception {
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private boolean doWriteMultiple(ChannelOutboundBuffer in, int writeSpinCount) throws Exception {
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if (PlatformDependent.hasUnsafe()) {
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// this means we can cast to IovArray and write the IovArray directly.
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IovArray array = IovArrayThreadLocal.get(in);
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int cnt = array.count();
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if (cnt >= 1) {
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// TODO: Handle the case where cnt == 1 specially.
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if (!writeBytesMultiple(in, array)) {
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if (!writeBytesMultiple(in, array, writeSpinCount)) {
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// was not able to write everything so break here we will get notified later again once
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// the network stack can handle more writes.
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return false;
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@ -293,7 +298,7 @@ public abstract class AbstractEpollStreamChannel extends AbstractEpollChannel {
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int cnt = in.nioBufferCount();
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if (cnt >= 1) {
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// TODO: Handle the case where cnt == 1 specially.
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if (!writeBytesMultiple(in, buffers, cnt, in.nioBufferSize())) {
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if (!writeBytesMultiple(in, buffers, cnt, in.nioBufferSize(), writeSpinCount)) {
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// was not able to write everything so break here we will get notified later again once
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// the network stack can handle more writes.
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return false;
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@ -88,14 +88,14 @@ public final class EpollDomainSocketChannel extends AbstractEpollStreamChannel {
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}
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@Override
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protected boolean doWriteSingle(ChannelOutboundBuffer in) throws Exception {
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protected boolean doWriteSingle(ChannelOutboundBuffer in, int writeSpinCount) throws Exception {
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Object msg = in.current();
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if (msg instanceof FileDescriptor && Native.sendFd(fd().intValue(), ((FileDescriptor) msg).intValue()) > 0) {
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// File descriptor was written, so remove it.
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in.remove();
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return true;
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}
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return super.doWriteSingle(in);
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return super.doWriteSingle(in, writeSpinCount);
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}
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@Override
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