Re: [QGIT PATCH/RFC]

[Marco Costalba <mcostalba@gmail.com>]

On Thu, Nov 5, 2009 at 11:37, Abdelrazak Younes <younes@lyx.org> wrote:
>
> I recompiled qgit with the Qt version and I didn't notice any performance
> problem with a big repo (Qt).
>

In git we don't need to compute hashes of sha strings because they are
already hashed !

That's the idea of using a custom hashing function that does nothing
but taking the first chars of the sha string. Instead the general
purpose Qt hashing must do real work because it has to work for any
string.

When I tested I _found_ a speed difference, but now I don't remember
of how much. Be sure you have warm cache when doing the test (press
F5) for few times to be sure all is in RAM.


> Just tell me if this is not interesting to you and I'll shut up :-)
>

No, it is very interesting indeed. My bad I have no time for  net access today.

If QByteArray is faster then QLatin1String() we should definitely
change. But if I don't remember wrong QLatin1String() is already
implemented above a QByteArray and the methods that we use are
inherited directly from a QByteArray, but I may be wrong. I don't have
access to the sources now. I only remember that when I implemented
that part it took a good amount of time and testing ;-)

Thanks
Marco