dongjoon-hyun commented on a change in pull request #29498:
URL: https://github.com/apache/spark/pull/29498#discussion_r474420370
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File path: docs/tuning.md
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@@ -264,6 +264,13 @@ parent RDD's number of partitions. You can pass the level
of parallelism as a se
or set the config property `spark.default.parallelism` to change the default.
In general, we recommend 2-3 tasks per CPU core in your cluster.
+Sometimes you may also need to increase directory listing parallelism when job
input has large number of directories,
+otherwise the process could take a very long time, especially when against
object store like S3.
Review comment:
What about remote HDFS? Since this looks like a general issue for remote
storage access. Especially, in disaggregated clusters where remote storage
(HDFS/S3) are used, can we generalize more like the following?
```
- especially when against object store like S3
- especially when against remote HDFS or S3 or in the disaggregated clusters
```
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