--predictable tries to eliminate all non-determinism. It's an umbrella flag that influences several parts of the system. In particular, it implies --single-threaded, which makes us compile all code on a single thread only. This of course changes timing significantly. In the default configuration, both Liftoff and TurboFan run concurrently. As soon as Liftoff is done, we start execution. TurboFan code is hot-swapped when it becomes ready (but will only be used for new function calls, i.e. no on-stack-replacement). Without --predictable, this makes it non-deterministic whether you execute Liftoff or TurboFan. You should actually see that when executing your test multiple times.
I am not 100% sure in which order things happen in predictable mode - but at least it should be a deterministic order. If you don't observe a slowdown, then it seems like TurboFan compilation always finishes before code is being executed. So maybe enabling predictable mode would also work for you, but just disabling Liftoff is the better solution, since it's way more specific. On Wed, Apr 8, 2020 at 1:51 PM Immanuel Haffner <[email protected]> wrote: > Disabling Liftoff is definitely a viable option for us right now. Related > to that, why am I not seeing a slowdown with `--predictable` and Liftoff > enabled? What is happening in predictable mode? > > Regarding 2), since we now have a workaround we can live with, I have more > important matters to tend to right now. I created an issue in our project > and maybe I will revisit it when I have some spare time. (Maybe we will > extend our system to produce minmal working examples so we can easily > report them to V8, who knows...?) > > Thanks a lot for the support. If there are anymore questions from your > side I will gladly try to answer them. > > -- > -- > v8-dev mailing list > [email protected] > http://groups.google.com/group/v8-dev > --- > You received this message because you are subscribed to the Google Groups > "v8-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/v8-dev/8e47c702-9e0b-4937-a309-0aa19c3bb412%40googlegroups.com > <https://groups.google.com/d/msgid/v8-dev/8e47c702-9e0b-4937-a309-0aa19c3bb412%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- Clemens Backes Software Engineer [email protected] Google Germany GmbH Erika-Mann-Straße 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Diese E-Mail ist vertraulich. Falls sie diese fälschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde. This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person. -- -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-dev/CAGO%3DqhAjnVENLDec%2BMnrJKTDsCmzp7jfuQaHvswaowNUSun%3Dmw%40mail.gmail.com.
