Weston Pace created ARROW-16138:
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Summary: [C++] Improve performance of ExecuteScalarExpression
Key: ARROW-16138
URL: https://issues.apache.org/jira/browse/ARROW-16138
Project: Apache Arrow
Issue Type: Improvement
Components: C++
Reporter: Weston Pace
One of the things we want to be able to do in the streaming execution engine is
process data in small L2 sized batches. Based on literature we might like to
use batches somewhere in the range of 1k to 16k rows. In ARROW-16014 we
created a benchmark to measure the performance of ExecuteScalarExpression as
the size of our batches got smaller. There are two things we observed:
* Something is causing thread contention. We should be able to get pretty
close to perfect linear speedup when we are evaluating scalar expressions and
the batch size fits entirely into L2. We are not seeing that.
* The overhead of ExecuteScalarExpression is too high when processing small
batches. Even when the expression is doing real work (e.g. copies,
comparisons) the execution time starts to be dominated by overhead when we have
10k sized batches.
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