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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2021/10/25 12:27:29 UTC
[GitHub] [flink] pnowojski commented on a change in pull request #17473: [FLINK-24470][runtime] EMA calculation move to BufferDebloater
pnowojski commented on a change in pull request #17473:
URL: https://github.com/apache/flink/pull/17473#discussion_r735539660
##########
File path: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/bufferdebloat/BufferDebloater.java
##########
@@ -94,10 +97,10 @@ public void recalculateBufferSize(long currentThroughput) {
return;
}
- lastBufferSize = newSize;
for (IndexedInputGate inputGate : inputGates) {
inputGate.announceBufferSize(newSize);
}
+ lastBufferSize = newSize;
Review comment:
Is this change relevant?
##########
File path: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/bufferdebloat/BufferSizeEMA.java
##########
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.flink.streaming.runtime.tasks.bufferdebloat;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/** Implementation of 'Exponential moving average' algorithm. */
+public class BufferSizeEMA {
+ private final int maxBufferSize;
+ private final int minBufferSize;
+ /** EMA algorithm specific constant which responsible for speed of reaction. */
+ private final double alpha;
+
+ private int lastBufferSize;
+
+ public BufferSizeEMA(int maxBufferSize, int minBufferSize, long numberOfSamples) {
+ this.maxBufferSize = maxBufferSize;
+ this.minBufferSize = minBufferSize;
+ alpha = 2.0 / (numberOfSamples + 1);
+ this.lastBufferSize = maxBufferSize;
+ }
+
+ /**
+ * Calculating the buffer size over total possible buffers size and number of buffers in use.
+ *
+ * @param totalBufferSizeInBytes Total buffers size.
+ * @param totalBuffers Total number of buffers in use.
+ * @return Throughput calculated according to implemented algorithm.
+ */
+ public int calculateBufferSize(long totalBufferSizeInBytes, int totalBuffers) {
+ checkArgument(totalBufferSizeInBytes >= 0, "Size of buffer should be non negative");
+ checkArgument(totalBuffers > 0, "Number of buffers should be positive");
+
+ // Limit the possible buffer size by twice of current buffer size in order to have the same
+ // changes speed for increasing and decreasing the size.
Review comment:
Can you elaborate on this explanation? Describe what was the problem with sudden throughput spike
?
##########
File path: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/bufferdebloat/BufferSizeEMA.java
##########
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.flink.streaming.runtime.tasks.bufferdebloat;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/** Implementation of 'Exponential moving average' algorithm. */
+public class BufferSizeEMA {
+ private final int maxBufferSize;
+ private final int minBufferSize;
+ /** EMA algorithm specific constant which responsible for speed of reaction. */
+ private final double alpha;
+
+ private int lastBufferSize;
+
+ public BufferSizeEMA(int maxBufferSize, int minBufferSize, long numberOfSamples) {
+ this.maxBufferSize = maxBufferSize;
+ this.minBufferSize = minBufferSize;
+ alpha = 2.0 / (numberOfSamples + 1);
+ this.lastBufferSize = maxBufferSize;
+ }
+
+ /**
+ * Calculating the buffer size over total possible buffers size and number of buffers in use.
+ *
+ * @param totalBufferSizeInBytes Total buffers size.
+ * @param totalBuffers Total number of buffers in use.
+ * @return Throughput calculated according to implemented algorithm.
+ */
+ public int calculateBufferSize(long totalBufferSizeInBytes, int totalBuffers) {
+ checkArgument(totalBufferSizeInBytes >= 0, "Size of buffer should be non negative");
+ checkArgument(totalBuffers > 0, "Number of buffers should be positive");
+
+ // Limit the possible buffer size by twice of current buffer size in order to have the same
+ // changes speed for increasing and decreasing the size.
+ long desirableBufferSize =
+ Math.min(totalBufferSizeInBytes / totalBuffers, 2L * lastBufferSize);
Review comment:
Shouldn't this be
```
Math.min(totalBufferSizeInBytes / totalBuffers, 2L * maxBufferSize);
```
?
Otherwise won't growing from `minBufferSize` to `maxBufferSize` be actually very slow compared to shrinking from `max` to `min`?
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