Very slow startup by the first run

[denizlitr]

Hi, I am writing a qt app for an embedded linux platform based on Freescale 5121 PPC core. The Qt version I am using is 4.7.2 static compiled.
The system boots over network and mounts a rootfs over nfs.

I made the following tests:
A small gui app showing only a couple of colored boxes takes over 20 secs to start by the first call. Wenn I quit the app and start it again, it starts instantly.

My first thought was the long load time over nfs (the staticly linked app is about 11 Megs), so I then copied the app into /tmp, which is mounted as tmpfs, meaning almost no load delays. This also didn't change the above behaviour.

Switching to dynamic linking didn't help.

Then I wrote the following app:

int main(....)
{
   QCoreApplication a(argc,argv);
   qDebug() << "test";
   return a.exec();
}

int main(....)
{
   QCoreApplication a(argc,argv);
   qDebug() << "test";
   return a.exec();
}

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this code ( resulting in about 2 Megs) did also show almost the same behaviour, except the delay was about 15 secs.

the apps are all release versions with -O2 compiled

a pure "C" HelloWorld programm with printf does start always instantly.

Any ideas, what to optimize/change or where to begin looking for the bottlenecks?