nswamy commented on a change in pull request #11204: Scala inference memory
leak fix
URL: https://github.com/apache/incubator-mxnet/pull/11204#discussion_r194773876
##########
File path: scala-package/core/src/main/scala/org/apache/mxnet/FeedForward.scala
##########
@@ -224,13 +224,24 @@ class FeedForward private(
var i = 0
while (data.hasNext && i != numBatch) {
val batch = data.next()
- i += 1
- ExecutorManager.loadData(batch, dataArrays)
- predExec.forward(isTrain = false)
- val padded = batch.pad
- val realSize = batchSize - padded
- for ((list, nd) <- outputs zip predExec.outputs) {
- list += nd.slice(0, realSize).copy()
+ try {
+ i += 1
+ ExecutorManager.loadData(batch, dataArrays)
+ predExec.forward(isTrain = false)
+ val padded = batch.pad
+ val realSize = batchSize - padded
+ for ((list, nd) <- outputs zip predExec.outputs) {
+ // The slice is being written to a value so that dispose can be
called after the copy.
+ // The one liner nd.slice().copy() leads to leaking the memory of
the slice.
+ val ndSliced = nd.slice(0, realSize)
+ try {
+ list += ndSliced.copy()
+ } finally {
+ ndSliced.dispose()
+ }
+ }
+ } finally {
+ batch.dispose()
Review comment:
shouldn't it be the dataArrays that needs to be disposed ? see
[loadData](https://github.com/apache/incubator-mxnet/blob/590ec3f508645ae06960a93293193f6280ed1c63/scala-package/core/src/main/scala/org/apache/mxnet/ExecutorManager.scala#L254)
and
[loadDatageneral](https://github.com/apache/incubator-mxnet/blob/590ec3f508645ae06960a93293193f6280ed1c63/scala-package/core/src/main/scala/org/apache/mxnet/ExecutorManager.scala#L227)
where its doing a copy from batch to dataArrays
I think we shouldn't dispose the original input from the Iterator, for
example if the user wants to use the same input on an another model
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