[Qt-interest] performance issue

[Paul Floyd]

Hi

I've just been doing a few tests on a small app that mostly does regex parsing
of a text file (56Mbyte). Times were as follows

Qt 4.1.4, GCC 3.4.3 22.6 sec
Qt 4.6.0, GCC 4.0.2 33.7 sec
Qt 4.6.0, Sun Studio 12u1 28.3 sec

all on Solaris 10 on SPARC.

I'm not surprised to see the difference between the 2nd and 3rd results. It's
the difference between the 1st and 2nd that I didn't expect.

My observations after profiling:
QIODevice::readline time increased by about 5.7 seconds
QRegExp::indexIn increased by about 1.6 seconds
(both inclusive times)

Heading the exclusive times league increases
take_deferred_signal (libc) increased by about 2.7 sec
lseek64 (libc) increased by about increased by about 2.1 sec.

take_deferred_signal seems to be called mainly from malloc (and realloc in case
3).
lseek64: case 2, QIODevice::atEnd; case 3, called by ftello64 and fseeko64.

Any comments on this?

I might do some more tests, but it gets a bit tedious building lots of different
Qt versions.
A+
Paul
-- 
Paul Floyd   http://paulf.free.fr