[Development] RFC: Proposal for a semi-radical change in Qt APIs taking strings

[Thiago Macieira]

On Saturday 17 October 2015 08:06:33 Marc Mutz wrote:
> > The word 'fanboys' disturbs me (I know you don't mean it that way) because
> > there are no 'hard' numbers on how 'bad' the current situation really is.
> > It would really be helpful to have an idea how 'real-world' applications
> > suffer from the current implementation of QString. That would give a very
> > good context to decide how Qt can help to leverage these problems.
> 
> If you want real-world numbers, follow the optimisations Milian did in moc. 
> IIRC, he documented the speedup.They are not (all) string-related, but I
> also don't claim that QStringView will single-handedly make your apps go
> faster. I wrote about QList already. There's more where these topics came
> from, but essentially they all boil down to: "minimise allocations".

On the other hand, note how real world numbers show that QtGui and QtWidgets 
consume a lot more CPU time than the combined time spent in malloc and QString 
operations.

Last time I profiled Qt Creator startup and parsing of projects, the two most 
expensive calls in QtCore were qHash and the SHA1 calculator. The former I've 
already fixed. The latter I was hoping that some colleagues would fix by 
creating an optimised library[1] we'd use but they refused to add SHA1 support 
to it.

[1] https://github.com/01org/tinycrypt
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center