mxsm commented on code in PR #5008:
URL: https://github.com/apache/rocketmq/pull/5008#discussion_r964369381
##########
common/src/main/java/org/apache/rocketmq/common/utils/ConcurrentHashMapUtils.java:
##########
@@ -39,10 +37,11 @@ private ConcurrentHashMapUtil() {
*/
public static <K, V> V computeIfAbsent(ConcurrentMap<K, V> map, K key,
Function<? super K, ? extends V> func) {
if (IS_JDK8) {
- V v, newValue;
- return ((v = map.get(key)) == null &&
- (newValue = func.apply(key)) != null &&
- (v = map.putIfAbsent(key, newValue)) == null) ? newValue : v;
+ V v = map.get(key);
+ if (null == v) {
+ v = map.computeIfAbsent(key, func);
+ }
+ return v;
Review Comment:
**JMH test code:**
```
@Warmup(iterations = 2, time = 5)
@Measurement(iterations = 3, time = 5)
@State(Scope.Benchmark)
@Fork(2)
public class ConcurrentHashMapBenchmark {
private static final String KEY = "mxsm";
private final ConcurrentHashMap<String, Object> concurrentMap = new
ConcurrentHashMap<>();
@Setup(Level.Iteration)
public void setup() {
concurrentMap.clear();
}
@Benchmark
@Threads(16)
public Object benchmarkGetBeforeComputeIfAbsent() {
return ConcurrentHashMapUtils.computeIfAbsent(concurrentMap, KEY,
key -> 1);
}
@Benchmark
@Threads(16)
public Object benchmarkComputeIfAbsent() {
return concurrentMap.computeIfAbsent(KEY, key -> 1);
}
}
```
**JDK1.8 JMH result**
```
root@GZYZFA00088591:/mnt/d/develop/github/benchmark/dledger-benchmark# java
-jar target/dledger-benchmarks.jar
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark
# JMH version: 1.35
# VM version: JDK 1.8.0_312, OpenJDK 64-Bit Server VM, 25.312-b07
# VM invoker: /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
# VM options: <none>
# Blackhole mode: full + dont-inline hint (auto-detected, use
-Djmh.blackhole.autoDetect=false to disable)
# Warmup: 2 iterations, 5 s each
# Measurement: 3 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 16 threads, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark:
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent
# Run progress: 0.00% complete, ETA 00:01:40
# Fork: 1 of 2
# Warmup Iteration 1: 42797877.446 ops/s
# Warmup Iteration 2: 41435241.953 ops/s
Iteration 1: 43157844.990 ops/s
Iteration 2: 43277492.813 ops/s
Iteration 3: 43040444.420 ops/s
# Run progress: 25.00% complete, ETA 00:01:15
# Fork: 2 of 2
# Warmup Iteration 1: 42515980.381 ops/s
# Warmup Iteration 2: 40242904.312 ops/s
Iteration 1: 39257833.798 ops/s
Iteration 2: 41280737.696 ops/s
Iteration 3: 41058950.020 ops/s
Result
"com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent":
41845550.623 ±(99.9%) 4492719.982 ops/s [Average]
(min, avg, max) = (39257833.798, 41845550.623, 43277492.813), stdev =
1602147.224
CI (99.9%): [37352830.640, 46338270.605] (assumes normal distribution)
# JMH version: 1.35
# VM version: JDK 1.8.0_312, OpenJDK 64-Bit Server VM, 25.312-b07
# VM invoker: /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
# VM options: <none>
# Blackhole mode: full + dont-inline hint (auto-detected, use
-Djmh.blackhole.autoDetect=false to disable)
# Warmup: 2 iterations, 5 s each
# Measurement: 3 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 16 threads, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark:
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent
# Run progress: 50.00% complete, ETA 00:00:50
# Fork: 1 of 2
# Warmup Iteration 1: 887931039.090 ops/s
# Warmup Iteration 2: 905677143.718 ops/s
Iteration 1: 996253036.363 ops/s
Iteration 2: 980599363.488 ops/s
Iteration 3: 929195073.587 ops/s
# Run progress: 75.00% complete, ETA 00:00:25
# Fork: 2 of 2
# Warmup Iteration 1: 810142530.110 ops/s
# Warmup Iteration 2: 872475730.400 ops/s
Iteration 1: 982104949.118 ops/s
Iteration 2: 1017002024.722 ops/s
Iteration 3: 1009650323.584 ops/s
Result
"com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent":
985800795.144 ±(99.9%) 87753464.794 ops/s [Average]
(min, avg, max) = (929195073.587, 985800795.144, 1017002024.722), stdev =
31293730.882
CI (99.9%): [898047330.350, 1073554259.937] (assumes normal distribution)
# Run complete. Total time: 00:01:41
REMEMBER: The numbers below are just data. To gain reusable insights, you
need to follow up on
why the numbers are the way they are. Use profilers (see -prof, -lprof),
design factorial
experiments, perform baseline and negative tests that provide experimental
control, make sure
the benchmarking environment is safe on JVM/OS/HW level, ask for reviews
from the domain experts.
Do not assume the numbers tell you what you want them to tell.
Benchmark Mode Cnt
Score Error Units
ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent thrpt 6
41845550.623 ± 4492719.982 ops/s
ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent thrpt 6
985800795.144 ± 87753464.794 ops/s
```
**JDK11 JMH result**
```
root@GZYZFA00088591:/mnt/d/develop/github/benchmark/dledger-benchmark# java
-jar target/dledger-benchmarks.jar
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.openjdk.jmh.util.Utils
(file:/mnt/d/develop/github/benchmark/dledger-benchmark/target/dledger-benchmarks.jar)
to method java.io.Console.encoding()
WARNING: Please consider reporting this to the maintainers of
org.openjdk.jmh.util.Utils
WARNING: Use --illegal-access=warn to enable warnings of further illegal
reflective access operations
WARNING: All illegal access operations will be denied in a future release
# JMH version: 1.35
# VM version: JDK 11.0.14.1, OpenJDK 64-Bit Server VM,
11.0.14.1+1-Ubuntu-0ubuntu1.18.04
# VM invoker: /usr/lib/jvm/java-11-openjdk-amd64/bin/java
# VM options: <none>
# Blackhole mode: full + dont-inline hint (auto-detected, use
-Djmh.blackhole.autoDetect=false to disable)
# Warmup: 2 iterations, 5 s each
# Measurement: 3 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 16 threads, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark:
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent
# Run progress: 0.00% complete, ETA 00:01:40
# Fork: 1 of 2
# Warmup Iteration 1: 752472650.077 ops/s
# Warmup Iteration 2: 758867890.461 ops/s
Iteration 1: 752371972.156 ops/s
Iteration 2: 728130288.110 ops/s
Iteration 3: 704975310.856 ops/s
# Run progress: 25.00% complete, ETA 00:01:16
# Fork: 2 of 2
# Warmup Iteration 1: 719451190.060 ops/s
# Warmup Iteration 2: 623980466.013 ops/s
Iteration 1: 696479838.494 ops/s
Iteration 2: 684992522.981 ops/s
Iteration 3: 705366498.201 ops/s
Result
"com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent":
712052738.466 ±(99.9%) 68156097.026 ops/s [Average]
(min, avg, max) = (684992522.981, 712052738.466, 752371972.156), stdev =
24305120.753
CI (99.9%): [643896641.441, 780208835.492] (assumes normal distribution)
# JMH version: 1.35
# VM version: JDK 11.0.14.1, OpenJDK 64-Bit Server VM,
11.0.14.1+1-Ubuntu-0ubuntu1.18.04
# VM invoker: /usr/lib/jvm/java-11-openjdk-amd64/bin/java
# VM options: <none>
# Blackhole mode: full + dont-inline hint (auto-detected, use
-Djmh.blackhole.autoDetect=false to disable)
# Warmup: 2 iterations, 5 s each
# Measurement: 3 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 16 threads, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark:
com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent
# Run progress: 50.00% complete, ETA 00:00:50
# Fork: 1 of 2
# Warmup Iteration 1: 700639928.397 ops/s
# Warmup Iteration 2: 591844187.371 ops/s
Iteration 1: 702190522.442 ops/s
Iteration 2: 714275280.316 ops/s
Iteration 3: 718153588.415 ops/s
# Run progress: 75.00% complete, ETA 00:00:25
# Fork: 2 of 2
# Warmup Iteration 1: 701145785.263 ops/s
# Warmup Iteration 2: 639685526.697 ops/s
Iteration 1: 703939208.535 ops/s
Iteration 2: 689861279.979 ops/s
Iteration 3: 645455868.007 ops/s
Result
"com.github.mxsm.dledger.benchmark.ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent":
695645957.949 ±(99.9%) 74379825.684 ops/s [Average]
(min, avg, max) = (645455868.007, 695645957.949, 718153588.415), stdev =
26524562.346
CI (99.9%): [621266132.265, 770025783.633] (assumes normal distribution)
# Run complete. Total time: 00:01:41
REMEMBER: The numbers below are just data. To gain reusable insights, you
need to follow up on
why the numbers are the way they are. Use profilers (see -prof, -lprof),
design factorial
experiments, perform baseline and negative tests that provide experimental
control, make sure
the benchmarking environment is safe on JVM/OS/HW level, ask for reviews
from the domain experts.
Do not assume the numbers tell you what you want them to tell.
Benchmark Mode Cnt
Score Error Units
ConcurrentHashMapBenchmark.benchmarkComputeIfAbsent thrpt 6
712052738.466 ± 68156097.026 ops/s
ConcurrentHashMapBenchmark.benchmarkGetBeforeComputeIfAbsent thrpt 6
695645957.949 ± 74379825.684 ops/s
```
on jdk11, ConcurrentHashMapBenchmark#benchmarkComputeIfAbsent and
ConcurrentHashMapBenchmark#benchmarkGetBeforeComputeIfAbsent run the same code.
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