lbradstreet commented on a change in pull request #8467:
URL: https://github.com/apache/kafka/pull/8467#discussion_r414100944
##########
File path: core/src/main/scala/kafka/log/LogManager.scala
##########
@@ -1003,9 +1003,17 @@ class LogManager(logDirs: Seq[File],
/**
* Map of log dir to logs by topic and partitions in that dir
*/
- private def logsByDir: Map[String, Map[TopicPartition, Log]] = {
- (this.currentLogs.toList ++ this.futureLogs.toList).toMap
- .groupBy { case (_, log) => log.parentDir }
+ def logsByDir: Map[String, Map[TopicPartition, Log]] = {
+ // This code is called often by checkpoint processes and is written in a
way that reduces
+ // allocations and CPU with many topic partitions.
+ // When changing this code please measure the changes with
org.apache.kafka.jmh.server.CheckpointBench
+ val byDir = new mutable.AnyRefMap[String,
mutable.AnyRefMap[TopicPartition, Log]]()
+ def addToDir(tp: TopicPartition, log: Log): Unit = {
+ byDir.getOrElseUpdate(log.parentDir, new
mutable.AnyRefMap[TopicPartition, Log]()).put(tp, log)
+ }
+ currentLogs.foreach { case (tp, log) => addToDir(tp, log) }
+ futureLogs.foreach { case (tp, log) => addToDir(tp, log) }
Review comment:
I tried out your suggestion and interestingly saw more allocations. Note
extreme use of the `var item` there in case there was an extra allocation there.
```
--- a/core/src/main/scala/kafka/log/LogManager.scala
+++ b/core/src/main/scala/kafka/log/LogManager.scala
@@ -1011,8 +1011,8 @@ class LogManager(logDirs: Seq[File],
def addToDir(tp: TopicPartition, log: Log): Unit = {
byDir.getOrElseUpdate(log.parentDir, new
mutable.AnyRefMap[TopicPartition, Log]()).put(tp, log)
}
- currentLogs.foreach { case (tp, log) => addToDir(tp, log) }
- futureLogs.foreach { case (tp, log) => addToDir(tp, log) }
+ currentLogs.foreachEntry(addToDir)
+ futureLogs.foreachEntry(addToDir)
byDir
}
diff --git a/core/src/main/scala/kafka/utils/Pool.scala
b/core/src/main/scala/kafka/utils/Pool.scala
index 964de7eae2..450f90611b 100644
--- a/core/src/main/scala/kafka/utils/Pool.scala
+++ b/core/src/main/scala/kafka/utils/Pool.scala
@@ -74,6 +74,15 @@ class Pool[K,V](valueFactory: Option[K => V] = None)
extends Iterable[(K, V)] {
def values: Iterable[V] = pool.values.asScala
def clear(): Unit = { pool.clear() }
+
+ def foreachEntry(f: (K, V) => Unit): Unit = {
+ val iter = iterator
+ var item: (K, V) = null
+ while(iter.hasNext) {
+ item = iter.next()
+ f(item._1, item._2)
+ }
+ }
```
CheckpointBench.measureCheckpointLogStartOffsets:·gc.alloc.rate.norm
3 2000 thrpt 15 1428889.965 ± 75131.113 B/op
vs this PR:
CheckpointBench.measureCheckpointLogStartOffsets:·gc.alloc.rate.norm
3 2000 thrpt 15 1284326.850 ± 75148.430 B/op
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