More integer allocations from StringLike#times after scala 2.12.8 upgrade #11547
Description
Hi Scala team,
We did a recent upgrade from scala 2.11.12 to 2.12.8, and we noticed that by running on 2.12.8 library, a lot more integers are allocated from calling StringLike#times method on top of a high stack trace(the stack trace we have seen by running async profiler has 46 levels, please see attachment 1).
However, when we try to run bench marks of just the times method in scala 2.11.12 and scala 2.12.8, scala 2.12.8 gave slightly better allocation rate and no integers allocated from running async profiler(please see attachment 2). This issue only happens when the times method is called at the end of a high stack trace.
Do you have any insights on what might cause this issue?
Thanks,
Jing
Attachment 1: Allocation profiling from calling StringLike#times class on top of a high stack trace(by Async Profiler)
--- **5636448352 bytes (31.43%), 3604 samples**
----- ----------------
[ 0] java.lang.Integer
[ 1] java.lang.Integer.valueOf
[ 2] scala.runtime.BoxesRunTime.boxToInteger
[ 3] scala.collection.immutable.Range.foreach
[ 4] scala.collection.immutable.StringLike.$times
[ 5] scala.collection.immutable.StringLike.$times$
[ 6] scala.collection.immutable.StringOps.$times
[ 7] com.twitter.finagle.integ.sim.HttpStreamingClientThroughputSim.$anonfun$request$1
[ 8] com.twitter.finagle.integ.sim.HttpStreamingClientThroughputSim$$Lambda$1140.1636868723.apply
[ 9] scala.collection.immutable.Stream$.$anonfun$fill$1
[10] scala.collection.immutable.Stream$$$Lambda$2178.1984970133.apply
[11] scala.collection.immutable.Stream$Cons.tail
[12] scala.collection.immutable.Stream$Cons.tail
[13] scala.collection.$plus$colon$.unapply
[14] com.twitter.io.SeqReader.read
[15] com.twitter.io.Reader$$anon$1.read
[16] com.twitter.finagle.netty4.http.Netty4StreamTransport$.continue$1
[17] com.twitter.finagle.netty4.http.Netty4StreamTransport$.$anonfun$streamOut$3
[18] com.twitter.finagle.netty4.http.Netty4StreamTransport$$$Lambda$2233.1867897542.apply
[19] com.twitter.util.Future.$anonfun$before$1
[20] com.twitter.util.Future$$Lambda$897.199150625.apply
[21] com.twitter.util.Promise$FutureTransformer.liftedTree1$1
[22] com.twitter.util.Promise$FutureTransformer.k
[23] com.twitter.util.Promise$Transformer.apply
[24] com.twitter.util.Promise$WaitQueue.com$twitter$util$Promise$WaitQueue$$run
[25] com.twitter.util.Promise$WaitQueue$$anon$1.run
[26] com.twitter.concurrent.LocalScheduler$Activation.run
[27] com.twitter.concurrent.LocalScheduler$Activation.submit
[28] com.twitter.concurrent.LocalScheduler.submit
[29] com.twitter.concurrent.Scheduler$.submit
[30] com.twitter.util.Promise$WaitQueue.runInScheduler
[31] com.twitter.util.Promise.continue
[32] com.twitter.util.Promise$Responder.respond
[33] com.twitter.util.Promise$Responder.respond$
[34] com.twitter.util.Promise.respond
[35] com.twitter.util.Future.proxyTo
[36] com.twitter.finagle.http2.transport.StreamTransportFactory$StreamTransport$$anon$8.run
[37] io.netty.util.concurrent.AbstractEventExecutor.safeExecute
[38] io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks
[39] io.netty.channel.epoll.EpollEventLoop.run
[40] io.netty.util.concurrent.SingleThreadEventExecutor$5.run
[41] io.netty.util.internal.ThreadExecutorMap$2.run
[42] java.util.concurrent.ThreadPoolExecutor.runWorker
[43] java.util.concurrent.ThreadPoolExecutor$Worker.run
[44] com.twitter.finagle.util.BlockingTimeTrackingThreadFactory$$anon$1.run
[45] io.netty.util.concurrent.FastThreadLocalRunnable.run
[46] java.lang.Thread.run
Attachment 2: Scala 2.11.12 vs. Scala 2.12.8 allocation profiling of calling StringLike#times alone(by Async Profiler)
[Scala 2.11.12]
**bytes percent samples top**
---------- ------- ------- ---
5989679736 58.85% 5418 char[]
4056970512 39.86% 3662 byte[]
50281024 0.49% 49 java.lang.String
17885768 0.18% 16 com.twitter.io.Buf$ByteArray
16199176 0.16% 15 scala.collection.immutable.Stream$$anonfun$fill$1
13047024 0.13% 12 java.lang.StringBuilder
7424176 0.07% 7 scala.Tuple2
6471168 0.06% 6 com.twitter.io.SeqReader
5770056 0.06% 6 com.twitter.util.Promise
5005960 0.05% 5 scala.Some
4565120 0.04% 4 com.twitter.util.ConstFuture
1905920 0.02% 2 scala.collection.immutable.StringOps
1037272 0.01% 493 java.util.TreeMap$Entry
756656 0.01% 361 java.util.TreeMap$KeyIterator
387136 0.00% 184 java.lang.management.MemoryUsage[]
250560 0.00% 120 java.util.Collections$UnmodifiableCollection$1
202440 0.00% 119 char[] (out)
152512 0.00% 60 byte[] (out)
33280 0.00% 16 java.util.TreeMap$KeySet
3024 0.00% 63 java.util.TreeMap (out)
2112 0.00% 1 java.util.TreeMap
32 0.00% 1 com.twitter.io.Buf$ByteArray (out)
24 0.00% 1 com.twitter.io.SeqReader (out)
24 0.00% 1 java.lang.String (out)
24 0.00% 1 scala.Tuple2 (out)
16 0.00% 1 scala.collection.immutable.StringOps (out)
[Scala 2.12.8]
**bytes percent samples top**
---------- ------- ------- ---
4938207856 57.09% 4449 char[]
3599997040 41.62% 3229 byte[]
22220392 0.26% 13 scala.collection.immutable.Range
20024544 0.23% 19 com.twitter.io.Buf$ByteArray
19762472 0.23% 19 java.lang.StringBuilder
15934968 0.18% 9 com.twitter.util.Promise
12808456 0.15% 11 scala.collection.immutable.StringOps
10042952 0.12% 5 scala.collection.immutable.Stream$Cons
7823048 0.09% 9 scala.collection.mutable.StringBuilder
1049896 0.01% 499 java.util.TreeMap$Entry
645568 0.01% 308 java.util.TreeMap$KeyIterator
326120 0.00% 155 java.lang.management.MemoryUsage[]
177600 0.00% 95 char[] (out)
143280 0.00% 59 byte[] (out)
125280 0.00% 60 java.util.Collections$UnmodifiableCollection$1
8256 0.00% 3 java.lang.String
4560 0.00% 95 java.util.TreeMap (out)
24 0.00% 1 scala.collection.immutable.StringLike$$Lambda$7 (out)