zzcclp commented on issue #4943:
URL:
https://github.com/apache/incubator-gluten/issues/4943#issuecomment-2003077901
> 原因：查询运行过程中，有26200次new byte[1024*1024] 操作，平均每个task有78次，总耗时8s, 而查询耗时也就30+s
>
>
问题：为什么会走带copy的OnHeapCopyShuffleInputStream，没走zero-copy的LowCopyNettyShuffleInputStream
>
> 调用链
>
> ```
> CHColumnarBatchSerializerInstance.deserializeStream
> CHStreamReader.CHStreamReader
> CHShuffleReadStreamFactory.create
> ```
>
> ```java
> public static ShuffleInputStream create(
> InputStream in, boolean forceCompress, boolean
isCustomizedShuffleCodec) {
> final InputStream unwrapped = unwrapInputStream(in, forceCompress,
isCustomizedShuffleCodec);
> if (unwrapped != null) {
> return createCompressedShuffleInputStream(in, unwrapped);
> }
> return new OnHeapCopyShuffleInputStream(in, false);
> }
>
> private static InputStream unwrapInputStream(
> InputStream in, boolean forceCompress, boolean
isCustomizedShuffleCodec) {
> if (forceCompress) {
> return unwrapSparkInputStream(in);
> } else if (isCustomizedShuffleCodec) {
> return unwrapSparkWithCompressedInputStream(in);
> }
> return null;
> }
> ```
>
> 由于我的local环境中并未设置celeborn作为shuffle manager,
因此最终走了OnHeapCopyShuffleInputStream。而OnHeapCopyShuffleInputStream目前的实现还不是很高效，最终导致了标题中描述的问题。
这里可能要看下你本地调用连，理应要走 LowCopyFileSegmentShuffleInputStream
这个，因为是从本地文件直接读取，按理走这里。
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