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https://issues.apache.org/jira/browse/ZOOKEEPER-2790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16030052#comment-16030052
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Abraham Fine commented on ZOOKEEPER-2790:
-----------------------------------------
Hi [~benedict jin]-
My understanding is that `LongAdder` and `AtomicLong` perform similarly under
low contention and `LongAdder` uses more memory.
Which usages of `AtomicLong` do you think cause enough performance problems to
justify this change?
> Should we consider using `LongAdder` instead of `AtomicLong`
> -------------------------------------------------------------
>
> Key: ZOOKEEPER-2790
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2790
> Project: ZooKeeper
> Issue Type: Improvement
> Components: server
> Affects Versions: 3.5.3
> Reporter: Benedict Jin
> Fix For: 4.0.0
>
>
> ```java
> // -Xmx512M -Xms512M -Xmn256M -XX:+AlwaysPreTouch -ea
> @Test
> public void pressureLongAdder() throws Exception {
> final LongAdder longAdder = new LongAdder();
> ExecutorService executorService = Executors.newCachedThreadPool();
> long startTime = System.currentTimeMillis();
> for (int i = 0; i < 100; i++) {
> executorService.submit(new Thread(() -> {
> for (int j = 0; j < 1000_0000; j++) {
> longAdder.increment();
> }
> System.out.print(String.format("%s %s \t",
> Thread.currentThread().getId(), longAdder.longValue()));
> /*
> 14 19607585 12 36445036 20 38985288 38 76821270
> 70 117094732 18 127252576
> 22 137043349 26 153411172 30 164051380 34 165971155
> 102 192241678 134 201104979
> 158 232657818 46 279030056 174 288502545 94 347965290
> 198 348060553 118 348087414
> 36 353092712 28 357762215 44 365464475 126 379518198
> 54 379623515 182 380077075
> 142 385263911 78 389013887 62 389085727 110 389122678
> 86 389920423 166 393535019
> 150 396382512 190 403100499 32 403161217 208 403197689
> 206 406065520 16 410725026
> 24 415347205 40 415379997 48 415733397 104 418507295
> 192 423244160 176 455793362
> 168 458311865 160 463028656 136 496375440 72 541243645
> 186 561877000 170 575352229
> 162 584152392 154 604552121 138 614092854 64 638151890
> 114 668705836 58 669235250
> 188 699213410 156 729222401 124 754336889 100 784326386
> 76 813479501 120 827569944
> 66 830236567 98 832153503 112 841408676 204 849520891
> 210 852391130 202 864804732
> 172 875603834 194 877222893 200 881090909 88 882809513
> 80 882846368 56 887174571
> 178 889682247 140 901357028 146 902169049 184 904540678
> 152 915608988 130 917896629
> 116 924616135 144 927674541 122 930399321 128 939791111
> 106 942656234 84 950848174
> 96 951904067 90 954910184 74 964338213 196 966487766
> 82 968307139 52 975854400
> 180 977385398 164 978882525 50 980896807 148 988292352
> 132 989090669 108 996891232
> 92 996921398 42 996938988 68 996953941 60 1000000000
> */
> }));
> }
> executorService.shutdown();
> while (!executorService.isTerminated()) {
> Thread.sleep(1);
> }
> long endTime = System.currentTimeMillis();
> System.out.println("\n" + (endTime - startTime)); // 3275 ms
> }
> // -Xmx512M -Xms512M -Xmn256M -XX:+AlwaysPreTouch -ea
> @Test
> public void pressureAtomicLong() throws Exception {
> final AtomicLong atomicLong = new AtomicLong();
> ExecutorService executorService = Executors.newCachedThreadPool();
> long startTime = System.currentTimeMillis();
> for (int i = 0; i < 100; i++) {
> executorService.submit(new Thread(() -> {
> for (int j = 0; j < 1000_0000; j++) {
> atomicLong.getAndIncrement();
> }
> System.out.print(String.format("%s %s \t",
> Thread.currentThread().getId(), atomicLong.longValue()));
> /*
> 12 390000000 28 390000000 44 390000000 20 390000000
> 26 390000000 18 390000000
> 80 390000000 56 390000000 96 390000000 24 390000000
> 88 390000000 72 390000000
> 22 390000000 118 390000000 54 390000000 142 390000000
> 70 390000000 86 390000000
> 182 390000000 110 390000000 62 390000000 78 390000000
> 102 390000000 158 390000000
> 150 390000000 46 390000000 38 390000000 126 390000000
> 94 390000000 134 390000000
> 14 390000000 48 390000000 40 390000000 32 390000000
> 34 390000000 64 390000000
> 42 390000000 36 390000000 16 390000000 180 416396554
> 204 419908287 196 425536497
> 92 732203658 30 733835560 202 733835559 210 733873571
> 146 733878564 186 733883527
> 170 733888686 76 733892691 84 733888815 148 733901560
> 162 733907032 172 733908079
> 52 733913280 116 733918421 124 733906868 164 733920945
> 132 733891348 68 733923672
> 108 733924928 156 733926091 60 733921998 140 733927257
> 188 733928891 154 733871822
> 194 733830477 178 733872527 100 733830322 106 748251688
> 144 1000000000 98 1000000000
> 58 1000000000 90 1000000000 130 1000000000 138 1000000000
> 114 1000000000 104 1000000000
> 168 1000000000 200 1000000000 184 1000000000 160 1000000000
> 174 1000000000 112 1000000000
> 190 1000000000 198 1000000000 82 1000000000 206 1000000000
> 166 1000000000 176 1000000000
> 136 1000000000 208 1000000000 74 1000000000 122 1000000000
> 152 1000000000 192 1000000000
> 120 1000000000 128 1000000000 66 1000000000 50 1000000000
> */
> }));
> }
> executorService.shutdown();
> while (!executorService.isTerminated()) {
> Thread.sleep(1);
> }
> long endTime = System.currentTimeMillis();
> System.out.println("\n" + (endTime - startTime)); // 19409 ms
> }
> ```
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