Agree that any additional object creation on a hot path could be a problem. So hot path should not contain stream API and any other potentially problem code (e.g. iterator instead of for by index).
On Wed, Sep 8, 2021 at 1:45 PM Pavel Tupitsyn <ptupit...@apache.org> wrote: > > Ok, maybe a total ban is overkill, but right now streams are used even on > some hot paths like getAllAsync [1]. > > Another issue is that Collectors.toList() and other variants don't accept > capacity, and we end up with unnecessary reallocations of underlying arrays. > > [1] > https://github.com/apache/ignite-3/blob/1d7d703ff2b18234b15a9a7b03104fbb73388edf/modules/table/src/main/java/org/apache/ignite/internal/table/KVBinaryViewImpl.java#L83 > > On Wed, Sep 8, 2021 at 1:06 PM Konstantin Orlov <kor...@gridgain.com> wrote: > > > Hi! > > > > Agree with Ivan that it’s an overkill. Code readability and > > maintainability should have > > the same priority as the performance (with some exceptions of course). > > > > BTW the result of your benchmark looks quite strange. The performance > > penalty on > > my laptop (Core i7 9750H, 6 cores up to 4.50 GHz) is 25%, not 8 times: > > > > Benchmark Mode Cnt Score Error Units > > JmhIncrementBenchmark.loopSum thrpt 10 32347.819 ± 676.548 ops/ms > > JmhIncrementBenchmark.streamSum thrpt 10 24459.196 ± 610.152 ops/ms > > > > > > -- > > Regards, > > Konstantin Orlov > > > > > > > On 8 Sep 2021, at 12:23, Ivan Bessonov <bessonov...@gmail.com> wrote: > > > > > > Hello Igniters, > > > > > > I object, banning streams is an overkill. I would argue that most of the > > > code > > > is not on hot paths and that allocations in TLAB don't create much > > pressure > > > on GC. > > > > > > Streams must be used cautiously, developers should know whether they > > > write hot methods or not. And if methods are not hot, code simplicity > > must > > > be > > > the first priority. I don't want Ignite 3 code to look like Ignite 2 > > code, > > > where > > > people would iterate over Lists using explicit access by indexes, > > because it > > > saves them a single Iterator allocation. That's absurd. > > > > > > ср, 8 сент. 2021 г. в 11:43, Pavel Tupitsyn <ptupit...@apache.org>: > > > > > >> Igniters, > > >> > > >> Java streams are known to be slower and cause more GC pressure than an > > >> equivalent loop. > > >> Below is a simple filter/map/reduce scenario (code [1]): > > >> > > >> * Benchmark Mode > > Cnt > > >> Score Error Units > > >> > > >> * StreamVsLoopBenchmark.loopSum thrpt > > 3 > > >> 7987.016 ± 293.013 ops/ms > > >> * StreamVsLoopBenchmark.loopSum:·gc.alloc.rate thrpt > > 3 > > >> ≈ 10⁻⁴ MB/sec > > >> * StreamVsLoopBenchmark.loopSum:·gc.count thrpt > > 3 > > >> ≈ 0 counts > > >> > > >> * StreamVsLoopBenchmark.streamSum thrpt > > 3 > > >> 1060.244 ± 36.485 ops/ms > > >> * StreamVsLoopBenchmark.streamSum:·gc.alloc.rate thrpt > > 3 > > >> 315.819 ± 10.844 MB/sec > > >> * StreamVsLoopBenchmark.streamSum:·gc.count thrpt > > 3 > > >> 55.000 counts > > >> > > >> Loop is several times faster and does not allocate at all. > > >> > > >> 1. Performance is one of the most important features of our product. > > >> 2. Most of our APIs will be on the hot path. > > >> > > >> One can argue about performance differences in real-world scenarios, > > >> but increasing GC pressure just to make the code a little bit nicer is > > >> unacceptable. > > >> > > >> I propose to ban streams usage in the codebase (except for the tests). > > >> > > >> Thoughts, objections? > > >> > > >> [1] https://gist.github.com/ptupitsyn/5934bbbf8f92ac4937e534af9386da97 > > >> > > > > > > > > > -- > > > Sincerely yours, > > > Ivan Bessonov > > > >
