ubuntu-phone team mailing list archive

[Thomas Voß <thomas.voss@xxxxxxxxxxxxx>]

On Fri, Oct 9, 2015 at 12:43 PM, Michael Zanetti
<michael.zanetti@xxxxxxxxxxxxx> wrote:
>
>
> On 09.10.2015 11:49, Pete Woods wrote:
>>
>>
>> On Thu, Oct 8, 2015 at 12:41 PM, Thomas Voß <thomas.voss@xxxxxxxxxxxxx
>> <mailto:thomas.voss@xxxxxxxxxxxxx>> wrote:
>>
>>     On Thu, Oct 8, 2015 at 1:36 PM, Michi Henning
>>     <michi.henning@xxxxxxxxxxxxx <mailto:michi.henning@xxxxxxxxxxxxx>>
>>     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.
>>
>> 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.
>>
>
> FWIW, Benjamin is experimenting with MeeGo's applauncherd/booster, which
> in principle does pretty much what you're describing. First tests do
> suggest that it does improve the situation quite a bit. Details still to
> be ironed out tho.
>

where "details" are actual security issues that we have to solve prior
to even start benchmarking :)

The difficulty is _not_  in keeping a set of pre-warmed processes
around to make app startup a rolling start.
But implementing a solution that is both secure *and* provides
significant improvements of app-startup time.

Cheers,

  Thomas

> Br,
> Michael
>
>
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