[SR-4666] Dictionary bridge is leaking memory

[palimondo]

Previous ID	SR-4666
Radar	rdar://problem/31788785
Original Reporter	@palimondo
Type	Bug
Status	Resolved
Resolution	Done

Environment

swift[master] at the time of report

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Bug, Leak
Assignee	@aschwaighofer
Priority	Medium

md5: 18d4ac6029a7d7afaf3318f44c1c2f65

relates to:

• SR-4667 Array is probably leaking memory
• SR-4668 NSStringRef is probably leaking memory

Issue Description:

Running DictionaryBridge performance test from Swift Benchmark Suite reveals a massive memory leak:

$ /usr/bin/time -lp $BUILD/bin/Benchmark_O --num-samples=1 DictionaryBridge
[...]
  17301504  maximum resident set size
[...] 
$ /usr/bin/time -lp $BUILD/bin/Benchmark_O --num-samples=3 DictionaryBridge
#,TEST,SAMPLES,MIN(us),MAX(us),MEAN(us),SD(us),MEDIAN(us)
[...]
  33226752  maximum resident set size
[...]
$ /usr/bin/time -lp $BUILD/bin/Benchmark_O --num-samples=20 DictionaryBridge
[...]
 137551872  maximum resident set size

number of iterations	MAX_RSS
1	17 MB
3	33 MB
20	137 MB

Same problem manifests when running benchmarks for ObjectiveCBridgeToNSDictionary and ObjectiveCBridgeToNSSet.

[belkadan]

@swift-ci create

[belkadan]

I suspect these all just need an autorelease pool around test runs.

[palimondo]

I hope you're right. But it is strange they vary so much between runs, too. Actually, it was the significant variance between runs with same --num-samples that triggered my investigation. I'm arguing in PR #8793 that benchmarks ought to be memory stable, and there should be no need to average MAX-RSS in the benchmark suite. Having non-deterministic behavior, even manifesting as variance in memory consumption seems like a symptom of a bug to me. Thoughts?

[aschwaighofer]

#9027

[aschwaighofer]

and #9031

[palimondo]

Verified fixed.

[palimondo]

These tests are now memory stable, the variance in MAX_RRS between runs as well as between different --num-samples is very low. CV=0,07%.

[palimondo]

aschwaighofer@apple.com (JIRA User) Reopening. Only DictionaryBridge was fixed. ObjectiveCBridgeToNSDictionary and ObjectiveCBridgeToNSSet in ObjectiveCBridging.swift still need similar fix.

[aschwaighofer]

Yep one more file

[aschwaighofer]

#9036