Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/21593#discussion_r196933769
--- Diff:
common/network-common/src/main/java/org/apache/spark/network/protocol/MessageWithHeader.java
---
@@ -137,30 +137,15 @@ protected void deallocate() {
}
private int copyByteBuf(ByteBuf buf, WritableByteChannel target) throws
IOException {
- ByteBuffer buffer = buf.nioBuffer();
- int written = (buffer.remaining() <= NIO_BUFFER_LIMIT) ?
- target.write(buffer) : writeNioBuffer(target, buffer);
+ // SPARK-24578: cap the sub-region's size of returned nio buffer to
improve the performance
+ // for the case that the passed-in buffer has too many components.
+ int length = Math.min(buf.readableBytes(), NIO_BUFFER_LIMIT);
+ ByteBuffer buffer = buf.nioBuffer(buf.readerIndex(), length);
--- End diff --
this pr is fixing a pretty serious issue, we know Wenbo is going to roll
this out immediately, and I suspect even more users will. this fix is also
"obviously correct" -- the followup here is not super complicated, but also
will be more prone to bugs. So I'm inclined to just get this in.
anyway if @WenboZhao can do the other part today, then sure, but I think we
should get this in quickly.
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