On Fri, Oct 9, 2015 at 11:49 AM, Pete Woods <[email protected]> wrote: > > > On Thu, Oct 8, 2015 at 12:41 PM, Thomas Voß <[email protected]> > wrote: >> >> On Thu, Oct 8, 2015 at 1:36 PM, Michi Henning >> <[email protected]> wrote: >> >> you can indeed build apps in C++ if you want, but C++ is more complex >> >> to >> >> understand and write (if you ever did a dynamic web page in your life >> >> you likely know the basics of js). C++ needs a (cross) compile >> >> environment set up while js means you can just dump a txt (well, .qml) >> >> file in place and it just works. Doing C++ is just a lot more work and >> >> while you can use C++ I think people find it easier to simply use js (I >> >> surely do, i can write a ready made QML app including rolling the click >> >> and uploading it to the store with a plain text editor within 20min, I >> >> (personally) cant do that in C++)) ... >> > >> > Writing a dynamic web page in C++ is a bit like writing a neural network >> > in COBOL. Don't. >> > >> > Would I write a device driver in JS? Probably not. >> > >> > Would I try to tighten a Phillips head screw with a nail file? Probably >> > not either. >> > >> > I think you get the drift… :-) >> > >> >> +1 :) >> >> Please note that qml and c++ components are happily mixed together >> with QML/Qt. If there is a serious performance issue with using pure >> QML, >> falling back to C++ is always possible. >> > > Remember everyone, that Android apps launch pretty quickly, and they are > Java based > (and were only natively compiled with the release of Lollipop's ART). > > This is achieved through the use of a "Zygote" process and some clever > copy-on-write > page management (I *think* using special kernel patches). There is always a > pre-warmed instance of the JVM ready, and it is forked each time a new app / > service > wants to launch. The page copy-on-write behaviour allows a new JVM instance > to be > spawned with almost no effort to the phone (you only copy the memory if you > alter the > Java runtime libs in some way, which is uncommon) and comes with large > memory savings. >
Well, and Dalvik has seen heavy optimization work for years. It is almost always possible to optimize a runtime, it just takes time and resources. For that, if developers want to do something now, they can just switch to C++ for the heavy lifting. @Zygote: Comes with its own set of issues, specifically regarding security. We investigated into the approach, but postponed implementation as we would have to do something along the lines of [1]. So it's not as easy as just copying Zygote :) > The summary of what I'm saying is the old adage "there are no slow > programming languages, > only slow programs". I think a lot of our app launch speed troubles could be > alleviated by > employing the same techniques that Google does. The answer to performance > issues > is rarely to "switch programming language", assuming you're using a language > that at > least has a JIT compiler. > In the limit case: certainly. However, calling out to more native* languages to carry out CPU-intensive tasks is common practice (in the Android world, too). Cheers, Thomas * where native usually is C/C++. [1] http://wenke.gtisc.gatech.edu/papers/morula.pdf > -Pete -- Mailing list: https://launchpad.net/~ubuntu-phone Post to : [email protected] Unsubscribe : https://launchpad.net/~ubuntu-phone More help : https://help.launchpad.net/ListHelp
