NicoK closed pull request #6553: [FLINK-10141][network] optimisations reducing
lock contention
URL: https://github.com/apache/flink/pull/6553
This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:
As this is a foreign pull request (from a fork), the diff is supplied
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diff --git
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
index 28f30209892..c4954c0fb6d 100644
---
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
+++
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
@@ -191,16 +191,16 @@ void retriggerSubpartitionRequest(int subpartitionIndex)
throws IOException, Int
checkError();
final Buffer next;
- final int remaining;
+ final boolean moreAvailable;
synchronized (receivedBuffers) {
next = receivedBuffers.poll();
- remaining = receivedBuffers.size();
+ moreAvailable = !receivedBuffers.isEmpty();
}
numBytesIn.inc(next.getSizeUnsafe());
numBuffersIn.inc();
- return Optional.of(new BufferAndAvailability(next, remaining >
0, getSenderBacklog()));
+ return Optional.of(new BufferAndAvailability(next,
moreAvailable, getSenderBacklog()));
}
//
------------------------------------------------------------------------
@@ -306,8 +306,8 @@ public void recycle(MemorySegment segment) {
int numAddedBuffers;
synchronized (bufferQueue) {
- // Important: check the isReleased state inside
synchronized block, so there is no
- // race condition when recycle and releaseAllResources
running in parallel.
+ // Similar to notifyBufferAvailable(), make sure that
we never add a buffer
+ // after releaseAllResources() released all buffers
(see below for details).
if (isReleased.get()) {
try {
inputGate.returnExclusiveSegments(Collections.singletonList(segment));
@@ -368,8 +368,13 @@ public boolean notifyBufferAvailable(Buffer buffer) {
checkState(isWaitingForFloatingBuffers,
"This channel should be waiting for
floating buffers.");
- // Important: double check the isReleased state
inside synchronized block, so there is no
- // race condition when notifyBufferAvailable
and releaseAllResources running in parallel.
+ // Important: make sure that we never add a
buffer after releaseAllResources()
+ // released all buffers. Following scenarios
exist:
+ // 1) releaseAllResources() already released
buffers inside bufferQueue
+ // -> then isReleased is set correctly
+ // 2) releaseAllResources() did not yet release
buffers from bufferQueue
+ // -> we may or may not have set isReleased yet
but will always wait for the
+ // lock on bufferQueue to release buffers
if (isReleased.get() ||
bufferQueue.getAvailableBufferSize() >= numRequiredBuffers) {
isWaitingForFloatingBuffers = false;
recycleBuffer = false; // just in case
@@ -385,10 +390,10 @@ public boolean notifyBufferAvailable(Buffer buffer) {
} else {
needMoreBuffers = true;
}
+ }
- if (unannouncedCredit.getAndAdd(1) == 0) {
- notifyCreditAvailable();
- }
+ if (unannouncedCredit.getAndAdd(1) == 0) {
+ notifyCreditAvailable();
}
return needMoreBuffers;
@@ -484,8 +489,8 @@ void onSenderBacklog(int backlog) throws IOException {
int numRequestedBuffers = 0;
synchronized (bufferQueue) {
- // Important: check the isReleased state inside
synchronized block, so there is no
- // race condition when onSenderBacklog and
releaseAllResources running in parallel.
+ // Similar to notifyBufferAvailable(), make sure that
we never add a buffer
+ // after releaseAllResources() released all buffers
(see above for details).
if (isReleased.get()) {
return;
}
@@ -510,33 +515,40 @@ void onSenderBacklog(int backlog) throws IOException {
}
public void onBuffer(Buffer buffer, int sequenceNumber, int backlog)
throws IOException {
- boolean success = false;
+ boolean recycleBuffer = true;
try {
+
+ final boolean wasEmpty;
synchronized (receivedBuffers) {
- if (!isReleased.get()) {
- if (expectedSequenceNumber ==
sequenceNumber) {
- int available =
receivedBuffers.size();
+ // Similar to notifyBufferAvailable(), make
sure that we never add a buffer
+ // after releaseAllResources() released all
buffers from receivedBuffers
+ // (see above for details).
+ if (isReleased.get()) {
+ return;
+ }
- receivedBuffers.add(buffer);
- expectedSequenceNumber++;
+ if (expectedSequenceNumber != sequenceNumber) {
+ onError(new
BufferReorderingException(expectedSequenceNumber, sequenceNumber));
+ return;
+ }
- if (available == 0) {
- notifyChannelNonEmpty();
- }
+ wasEmpty = receivedBuffers.isEmpty();
+ receivedBuffers.add(buffer);
+ recycleBuffer = false;
+ }
- success = true;
- } else {
- onError(new
BufferReorderingException(expectedSequenceNumber, sequenceNumber));
- }
- }
+ ++expectedSequenceNumber;
+
+ if (wasEmpty) {
+ notifyChannelNonEmpty();
}
- if (success && backlog >= 0) {
+ if (backlog >= 0) {
onSenderBacklog(backlog);
}
} finally {
- if (!success) {
+ if (recycleBuffer) {
buffer.recycleBuffer();
}
}
diff --git
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
index 2e7d076f3f8..f51dc7417ab 100644
---
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
+++
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
@@ -545,7 +545,7 @@ public void requestPartitions() throws IOException,
InterruptedException {
currentChannel = inputChannelsWithData.remove();
enqueuedInputChannelsWithData.clear(currentChannel.getChannelIndex());
- moreAvailable = inputChannelsWithData.size() >
0;
+ moreAvailable =
!inputChannelsWithData.isEmpty();
}
result = currentChannel.getNextBuffer();
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