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Benchmarking with JMH (riviera dev 2017)
- 1. Kickass benchmarking with JMH Leonardo F. Gomes Nenad Bogojevic 0
- 3. Premature optimization Donald Knuth, 1974 is the root of all evil 2
- 4. Donald E. Knuth Professor Emeritus at Stanford University ACM Grace Murray Hopper Award Turing Award Author of The Art Of Computer Programming Creator of TeX 3
- 5. 4
- 6. Donald E. Knuth We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. 5
- 7. Donald E. Knuth A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. 6
- 8. Donald E. Knuth It is often a mistake to make a priori judgements about what parts of a program are really critical. 7
- 9. Donald E. Knuth The universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail. 8
- 10. Good programmers measure before optimizing 9
- 13. Why? 12
- 14. Warmup phase 13
- 15. Java source code Bytecodes HotSpot Java VM compile execute _Ahead-of- time _Using javac _Instructions for an abstract machine 14
- 16. Bytecodes HotSpot Java VM Interpreter Heap Stack Garbage collector execute access access manage vC1 C2 Machine code Debug info Compiled method Object maps compile produce Compilation system 15
- 19. ©2016AmadeusITGroupanditsaffiliatesandsubsidiaries Don’t roll out your own benchmarking harness 18
- 20. JMH is your friend 19
- 26. JMH is for benchmarking what JUnit is for unit testing 25
- 28. Macro 1 … 1000s Milli 1 … 1000ms Micro 1 … 1000us Nano 1 … 1000ns 27 Granularity
- 29. Benchmark modes Throughput ops/time_unit AverageTime time/operation SampleTime percentiles SingleShotTime cold performance 28
- 33. Multithreading made easy results are aggregated for you 32
- 35. 34 table lock thread 0 get ( key0 ) thread 1 get ( key1 ) put ( key0, value0 ) put ( key1, value1 ) lock (thread 0)
- 37. 36 Segment Segment Segment Segment lock lock lock lock thread 0 put ( key0, value0) segmentFor ( hash0 ) thread 1 put ( key1, value1) segmentFor ( hash1 ) thread 2 put ( key2, value2) segmentFor ( hash2 ) lock (thread 0) lock (thread 1)
- 38. 37 Segment Segment Segment Segment lock lock lock lock thread 0 get ( key0 ) segmentFor ( hash0 ) thread 2 get ( key2 ) segmentFor ( hash2 ) read volatile read volatile
- 40. Built-in profilers can show If compilation is happening while measuring If class loading is happening while measuring How much object allocation is happening Which methods are consuming CPU time 39
- 41. External profilers can be used Linux perf_events Windows xperf Java Mission Control (pluggable) Yourkit, etc. 40
- 44. Verify that new code matches expectations Check that no regression is introduced Validate optimization ideas Cover performance fixes with related test
- 49. Care about a warmup phase Reduce noise Define regression Make sure backlog is handled
- 50. Key takeaways 50 Benchmark is tricky Measure before optimizing JMH helps a lot
- 51. • Caliper: https://www.flickr.com/photos/andrewthecook/14026422669/sizes/l • Geometric forms: https://www.flickr.com/photos/internetarchivebookimages/14753972274/sizes/l • Metric tape: https://www.flickr.com/photos/ilianov/3345314090/sizes/l/ • Mountain: https://www.flickr.com/photos/pthread/8151096195/sizes/l • Friends: https://www.flickr.com/photos/livenature/13895494231/sizes/l • Root: https://www.flickr.com/photos/paperpariah/19937816358/sizes/l/ • Knuth: https://www.flickr.com/photos/ioerror/56360019/sizes/l • Warmup: https://www.flickr.com/photos/komunews/2085730526/sizes/o/ • Multithreading: https://www.flickr.com/photos/slimjim/4329655445/sizes/l • Stop: https://www.flickr.com/photos/thematthewknot/3924980314/sizes/l • Boats: https://www.flickr.com/photos/cuppini/8465318134/sizes/l • Next steps: https://www.flickr.com/photos/gebagia/22346547334/sizes/l • Marines: https://www.flickr.com/photos/dvids/14007373489/sizes/l • Artic ice: https://commons.wikimedia.org/wiki/File:ICESCAPE.jpg • Demo time: https://www.flickr.com/photos/abstractbynature/6111219203 • Blue sky: https://www.flickr.com/photos/foctavian/16371691937/ 51
- 52. Questions? 52
Editor's Notes
- Motivation: Professional programmers should take responsibility on the performance of the code that they are developing. Performance is frequently something that is overlooked until last phases of the development process, whereas it should actually be integrated in the development process. TODO: Add some motivation around environmental benefits.
- This catching phrase is usually used without much context. Just like biblical citations it can lead to religious wars. Let’s check the context around that phrase.
- This catching phrase is usually used without much context. Just like biblical citations it can lead to religious wars. Let’s check the context around that phrase.
- Let’s put some context around that citation. Look into what’s written before and after that phrase in the paper where it appeared. Knuth is the guy who said that. There’s some polemic about whether the quote is originally from Knuth or if he was citing Tony Hoare. This article tries to ”prove” that it’s actually from Knuth: https://shreevatsa.wordpress.com/2008/05/16/premature-optimization-is-the-root-of-all-evil/
- A little bit of context: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgements about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail.” Page 268 Donald Knuth Structured programming with go to statements Computing Surveys, Vol. 6, No. 4, December 1974 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.6084&rep=rep1&type=pdf
- A little bit of context: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgements about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail.” Page 268 Donald Knuth Structured programming with go to statements Computing Surveys, Vol. 6, No. 4, December 1974 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.6084&rep=rep1&type=pdf
- A little bit of context: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgements about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail.” Page 268 Donald Knuth Structured programming with go to statements Computing Surveys, Vol. 6, No. 4, December 1974 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.6084&rep=rep1&type=pdf
- A little bit of context: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgements about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail.” Page 268 Donald Knuth Structured programming with go to statements Computing Surveys, Vol. 6, No. 4, December 1974 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.6084&rep=rep1&type=pdf
- A little bit of context: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunity in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgements about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that the intuitive guesses fail.” Page 268 Donald Knuth Structured programming with go to statements Computing Surveys, Vol. 6, No. 4, December 1974 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.6084&rep=rep1&type=pdf
- Summary of what Knuth said
- https://commons.wikimedia.org/wiki/File:ICESCAPE.jpg
- Now you’re all convinced that you should be measuring the performance of your code. But wait, don’t just put timers on your unit-tests .
- Now you’re all convinced that you should be measuring the performance of your code. But wait, don’t just put timers on your unit-tests .
- Explain how code is initially interpreted; Then, compiled at runtime; Then, it runs in compiled mode.
- Explain how code is initially interpreted; Then, compiled at runtime; Then, it runs in compiled mode.
- Explain how code is initially interpreted; Then, compiled at runtime; Then, it runs in compiled mode.
- Branch prediction Loop unrolling Dead code elimination Autobox elimitation Constant propagation Null check elimination Algebraic simplification Devirtualisation Range check elimitation Etc.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you. The thread scope matches well the concept of application server, because usually Java app servers have scope per thread. This would be like processing 20 requests in parallel. Benchmark scope would be a cache that all your requests are accessing. It should be guarded by synchronization mechanisms to make sure that it remains consistent.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- Write to a volatile happens-before every subsequent read of that volatile
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- Instead of using a single lock for the shared data, the shared data is segmented with each segment having its own lock. Uncontended lock acquisition is very cheap; it's the contented locks that cause scalability issues. With a different lock for each partition, ConcurrentHashMap effectively reduces how often a lock is requested by the number of partitions. You can think of ConcurrentHashMap as made up of n separate hash tables.
- Write to a volatile happens-before every subsequent read of that volatile
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- JMH is an open-source project that does exactly that. It’s part of the OpenJDK project and we will see how it can help you.
- https://github.com/chrishantha/jfr-flame-graph
- http://netty.io/wiki/microbenchmarks.html https://github.com/grpc/grpc-java/tree/master/benchmarks/src/jmh https://github.com/akka/akka/tree/master/akka-bench-jmh https://github.com/SonarSource/sslr/blob/master/sslr-benchmarks/src/main/java/org/sonar/sslr/benchmarks/RecursiveRuleBenchmark.java https://github.com/droolsjbpm/kie-benchmarks/blob/master/drools-benchmarks/src/main/java/org/drools/benchmarks/session/InsertFireLoopBenchmark.java https://github.com/finagle/finagle-serial#benchmarks
- LMAX: Our micro-benchmarks currently take over an hour to run, though with more hardware we could run them in parallel to improve this. That's still not bad, but for comparison, our suite of ~11k acceptance tests only takes ~25mins...
- Reduce noise / Isolate your benchmarks as much as possible (using cpu isolation, sched_setaffinity); Care about a correct warmup phase / Give benchmarks enough time to run; Don't do nanosecond per operation benchmarks in Continuous integration; Define regression / Some variance is expected; Define well your baseline; Differentiate inter-version, intra-version regressions; Make sure issues backlog is tracked and handled.