Andrew Or created SPARK-12473:
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Summary: Reuse serializer instances for performance
Key: SPARK-12473
URL: https://issues.apache.org/jira/browse/SPARK-12473
Project: Spark
Issue Type: Bug
Components: Spark Core
Affects Versions: 1.6.0
Reporter: Andrew Or
Assignee: Andrew Or
After commit de02782 of page rank regressed from 242s to 260s, about 7%.
The commit added 26 types to register every time we create a Kryo serializer
instance. I ran a small microbenchmark to prove that this is noticeably
expensive:
{code}
import org.apache.spark.serializer._
import org.apache.spark.SparkConf
def makeMany(num: Int): Long = {
val start = System.currentTimeMillis
(1 to num).foreach { _ => new KryoSerializer(new SparkConf).newKryo() }
System.currentTimeMillis - start
}
// before commit de02782, averaged over multiple runs
makeMany(5000) == 1500
// after commit de02782, averaged over multiple runs
makeMany(5000) == 2750
{code}
Since we create multiple serializer instances per partition, this means a
5000-partition stage will unconditionally see an increase of > 1s for the
stage. In page rank, we may run many such stages.
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