mridulm commented on code in PR #2462:
URL: https://github.com/apache/celeborn/pull/2462#discussion_r1568117997
##########
client/src/main/scala/org/apache/celeborn/client/ChangePartitionManager.scala:
##########
@@ -79,14 +81,17 @@ class ChangePartitionManager(
batchHandleChangePartitionExecutors.submit {
new Runnable {
override def run(): Unit = {
- val distinctPartitions = requests.synchronized {
- // For each partition only need handle one request
- requests.asScala.filter { case (partitionId, _) =>
-
!inBatchPartitions.get(shuffleId).contains(partitionId)
- }.map { case (partitionId, request) =>
- inBatchPartitions.get(shuffleId).add(partitionId)
- request.asScala.toArray.maxBy(_.epoch)
- }.toArray
+ val distinctPartitions = {
+ requests.asScala.map { case (partitionId, request) =>
+ locks(partitionId % locks.length).synchronized {
+ if (!inBatchPartitions.contains(partitionId)) {
+ inBatchPartitions.get(shuffleId).add(partitionId)
+ Some(request.asScala.toArray.maxBy(_.epoch))
+ } else {
+ None
+ }
+ }
+ }.filter(_.isDefined).map(_.get).toArray
Review Comment:
I am not so sure of this change - it feels like it will have a lot more
contention - as each entry in the `requests` map will need to acquire a lock -
while uncontented locks are cheap to acquire, it is not zero cost still.
If you have a test bed to validate perf, how about this ?
```
val batchPartitions = inBatchPartitions.get(shuffleId)
val distinctPartitions = requests.synchronized {
// For each partition only need handle one request
requests.asScala.filter { case (partitionId, _) =>
!batchPartitions.contains(partitionId)
}.map { case (partitionId, request) =>
batchPartitions.add(partitionId)
request.asScala.maxBy(_.epoch)
}.toArray
}
```
##########
client/src/main/scala/org/apache/celeborn/client/ChangePartitionManager.scala:
##########
@@ -151,7 +156,7 @@ class ChangePartitionManager(
oldPartition,
cause)
- requests.synchronized {
+ locks(partitionId % locks.length).synchronized {
if (requests.containsKey(partitionId)) {
requests.get(partitionId).add(changePartition)
logTrace(s"[handleRequestPartitionLocation] For $shuffleId, request
for same partition" +
Review Comment:
We could replace this with a `computeIfAbsent` ?
Something like:
```
requests.synchronized {
var newEntry = false
val set = requests.computeIfAbsent(partitionId, (v1: Integer) => {
// If new slot for the partition has been allocated, reply and
return.
// Else register and allocate for it.
getLatestPartition(shuffleId, partitionId, oldEpoch).foreach {
latestLoc =>
context.reply(
partitionId,
StatusCode.SUCCESS,
Some(latestLoc),
lifecycleManager.workerStatusTracker.workerAvailable(oldPartition))
logDebug(s"New partition found, old partition
$partitionId-$oldEpoch return it." +
s" shuffleId: $shuffleId $latestLoc")
return
}
newEntry = true
new util.HashSet[ChangePartitionRequest]()
})
set.add(changePartition)
if (!newEntry) {
logTrace(s"[handleRequestPartitionLocation] For $shuffleId, request
for same partition" +
s"$partitionId-$oldEpoch exists, register context.")
}
}
```
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