feat: Record Arrow FFI metrics #1128
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| @@ -88,6 +90,7 @@ impl ScanExec { | |||
| ) -> Result<Self, CometError> { | |||
| let metrics_set = ExecutionPlanMetricsSet::default(); | |||
| let baseline_metrics = BaselineMetrics::new(&metrics_set, 0); | |||
| let arrow_ffi_time = MetricBuilder::new(&metrics_set).subset_time("arrow_ffi_time", 0); | |||
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I see now that this isn't just FFI time. It is the cost of calling CometBatchIterator.next() so includes the cost of that method getting the next input batch as well as the FFI export cost ...
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Moving this to draft for now while I think about this more
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I'd be astonished if arrow_ffi has a substantial cost. It is, after all, zero-copy.
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It is zero copy for the data buffers, but the schema does get serialized with each batch. However, it does not look to be an issue after all
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but the schema does get serialized with each batch
fair point
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lgtm thanks @andygrove
one thing I'd like to mention are you planning to have it permanently or enable this internal metrics based on some spark key so as to spend resources on metrics only when its really needed
Which issue does this PR close?
N/A
Rationale for this change
This is a subset of #1111, separated out to make reviews easier.
What changes are included in this PR?
Record time spent performing Arrow FFI to transfer batches between JVM and Rust code.
Note that these timings won't be fully exposed to Spark UI until we merge #1111.
How are these changes tested?