I don't think we should ban anything. Streams API is just a tool in the toolbox - it should be used appropriately. It's up to the contributor and reviewer(s) to identify whether a particular usage might cause performance issues.
-Val On Wed, Sep 8, 2021 at 8:01 AM Alexander Polovtcev <alexpolovt...@gmail.com> wrote: > -1 > I think that it is not very productive to assume that 100% of your code is > on the hot path, it would be impossible to write and maintain. Humans are > not very good at guessing where the performance bottlenecks are, so the > performance of the possible hot paths should be measured first and only > then optimized and documented. > > On Wed, Sep 8, 2021 at 5:53 PM Ivan Pavlukhin <vololo...@gmail.com> wrote: > > > Does not this trivial strategy work for us? > > https://wiki.c2.com/?OptimizeLater > > > > 2021-09-08 13:52 GMT+03:00, Andrey Gura <ag...@apache.org>: > > > 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 > > >> > > > >> > > > > > > > > > > -- > > > > Best regards, > > Ivan Pavlukhin > > > > > -- > With regards, > Aleksandr Polovtcev >
