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[SPARK-14242][CORE][Network] avoid copy in compositeBuffer for frame decoder #12038

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[SPARK-14242][CORE][Network] avoid copy in compositeBuffer for frame decoder #12038

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spark-14242 avoid using compositeBuffer for frame decoder
liyezhang556520 Mar 29, 2016
1eacf55
use compositeByteBuf.addComponents to for netty frame buffer
liyezhang556520 Mar 30, 2016
80f7573
only set maxNumComponents for compositeByteBuffer to solve the issue
liyezhang556520 Mar 31, 2016
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2 changes: 1 addition & 1 deletion common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
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Expand Up @@ -140,7 +140,7 @@ private ByteBuf decodeNext() throws Exception {
}

// Otherwise, create a composite buffer.
CompositeByteBuf frame = buffers.getFirst().alloc().compositeBuffer();
CompositeByteBuf frame = buffers.getFirst().alloc().compositeBuffer(Integer.MAX_VALUE);
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@liyezhang556520 liyezhang556520 Mar 29, 2016

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actually we can set the maxNumComponents for compositeBuffer to avoid consolidate underlying, such as CompositeByteBuf frame = buffers.getFirst().alloc().compositeBuffer(Integer.MAX_VALUE);, but this might be not a good choice.

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@vanzin vanzin Mar 29, 2016

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Why is it not a good choice? With your change, you're replacing "maybe copy multiple times" with "always copy once". If there's a way to avoid the copy altogether, why not do it?

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@liyezhang556520 liyezhang556520 Mar 30, 2016

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@vanzin , I'm not sure why Netty underlying set a maximum number components (max size is Integer.MAX_VALUE), and the default value is only 16, this seems very small for consolidation. Will it occurs other problem when there are too many small buffers under compositeBuffer? Is that why it will consolidate when the small buffer number reaches the maxNumCompnent?

while (remaining > 0) {
ByteBuf next = nextBufferForFrame(remaining);
remaining -= next.readableBytes();
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