Github user Ngone51 commented on a diff in the pull request:
https://github.com/apache/spark/pull/22163#discussion_r211954019
--- Diff:
core/src/main/java/org/apache/spark/shuffle/sort/ShuffleExternalSorter.java ---
@@ -206,14 +211,21 @@ private void writeSortedFile(boolean isLastFile) {
long recordReadPosition = recordOffsetInPage + uaoSize; // skip over
record length
while (dataRemaining > 0) {
final int toTransfer = Math.min(diskWriteBufferSize,
dataRemaining);
- Platform.copyMemory(
- recordPage, recordReadPosition, writeBuffer,
Platform.BYTE_ARRAY_OFFSET, toTransfer);
- writer.write(writeBuffer, 0, toTransfer);
+ if (bufferOffset > 0 && bufferOffset + toTransfer >
DISK_WRITE_BUFFER_SIZE) {
--- End diff --
Not a bad idea, but codes here may not work as you expect. If we got a
record with size `X` < `diskWriteBufferSize `(same as `DISK_WRITE_BUFFER_SIZE
`), then we will only call `writer.write()` once. And if we got a record with
size `Y` >= `diskWriteBufferSize `, then we will call `writer.write()` for
(`Y` + `diskWriteBufferSize ` - 1) / `diskWriteBufferSize` times. And this do
not change with the new code.
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