[PATCH] speedup in KMimeTypeFactory?

Olivier Goffart ogoffart at kde.org
Sun Oct 19 15:23:31 BST 2008

Le dimanche 19 octobre 2008, Matt Rogers a écrit :
> Hi,
> The attached patch makes some changes to the matchFileName function in
> kmimetypefactory.cpp which gets called a lot, especially when browsing
> files in the file manager when trying to open a file.
> Depending on how you read the callgrind output, it's either a 5% (incl.
> column) speedup or a 0.5% (self column) speedup. I can't remember which is
> the more important number.

The 'incl' is the most important.  The self doesn't matter at all (it's 
included in the 'incl' anyway)

I would say that what you have to compare is the 'Incl.' absolute cost divided 
by the 'Called'

Caching the indexOf('[') certainly helps.

But changing from the operator[] to startsWith/endsWith is probably slower 
(the operator[] is inline and fast, while endsWith do lot of comparison and 
don't know that we are comparing only one byte)

I don't know if the static QChar really helps.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part.
URL: <http://mail.kde.org/pipermail/kde-core-devel/attachments/20081019/9b5d4b57/attachment.sig>

More information about the kde-core-devel mailing list