Has anyone else experienced issues with NSObjects not being deallocated properly? I have a function...

# kotlin-native

[Sam Schilling]

Has anyone else experienced issues with NSObjects not being deallocated properly?

I have a function that is called in a loop which allocates an NSObject (NSProcessInfo) but it never gets deallocated

My loop runs for 150 ms and during that time application memory usage typically rises by ~50 MB, and when profiling I see it is because there are thousands of NSProcessInfo objects that never get deallocated (each one is only 4 KB)

fun elapsedRealtime() = (NSProcessInfo().systemUptime * 1_000)

val startTime = elapsedRealtime()
var currentTime = startTime
while (currentTime - startTime < 150) {
    currentTime = elapsedRealTime()
}

I would think NSProcessInfo objects should automatically be deallocated each time elapsedRealtime completes since the reference count would be 0, but I am unsure how Kotlin’s GC interacts with Swift/Objective-C’s ARC

If I change the loop to run for 25 seconds for example my memory usage shoots up nearly 500 MB.

This is running on macOS 10.14.6

[Sam Schilling]

FWIW, I was able to greatly decrease the memory footprint by surrounding the function in an autorelease pool, but it still seems to hold onto a bunch of the objects without releasing, just less than before

[Sam Schilling]

fun elapsedRealTime() = autoreleasepool { NSProcessInfo().systemUptime * 1_000 }
In this case I can run for 25 seconds and only increase memory by about 7 MB (as opposed to 500 MB previously), but still that 7 MB never goes away after the fact

[olonho]

insert GC call <https://github.com/JetBrains/kotlin-native/blob/8e0e346492436cc9c40d87f38926e841954d1d4e/runtime/src/main/kotlin/kotlin/native/internal/GC.kt#L30> if you need to force collection, K/N uses delayed reference counter, so some memory may add up

[Sam Schilling]

@olonho I have tried that and it does not free up any of the memory

[Sam Schilling]

I even tried calling GC.start() first since it says collect will not do anything if it is stopped

[olonho]

How do you measure?

[Sam Schilling]

Mac Activity Monitor

[Sam Schilling]

Shows the memory gradually go up to 500 MB as soon as my loop starts, and the program continues to execute afterwards but memory never goes down even after GC collect call

[Sam Schilling]

I am writing a framework that is used in Swift as well and using the Xcode profiler to view allocations I see that the @autoreleasepool content section is never cleared

[Sam Schilling]

@olonho Created a gist, maybe you can try to reproduce with it?
https://gist.github.com/sschilli/5692c4582a85daec9a3ace186d8b431c

[Sam Schilling]

I just came across something interesting… if I call GC.collect after the loop body, memory usage grows very quickly, up to 500 MB:

while (currentTime - startTime < 25_000L) {
    currentTime = timer.elapsedRealtime()
}
GC.collect()

[Sam Schilling]

However if I call it inside the loop body, it grows much slower, up to only 8 MB by the time 25 seconds expires:

while (currentTime - startTime < 25_000L) {
    currentTime = timer.elapsedRealtime()
    GC.collect()
}

Can anyone explain this disparity?

[Sam Schilling]

@olonho I didn’t think GC.collect would be context dependent?

[Sam Schilling]

Seems to imply a memory leak

[Sam Schilling]

Either way though memory usage continues to grow unbounded despite GC.collect call, just because NSProcessInfo isn’t deallocated properly

[olonho]

Please file an issue, but note, that macOS memory manager doesn’t guarantee, that even after freeing OS footprint reduces, so real marker if leak is evergrowing memory usage or seen in analysis by tools like valgrind