Version:            (using KDE 4.0.1)
Installed from:    Fedora RPMs
OS:                Linux

On my machine, Okular's PDF rendering is much slower than with KPDF. This is especially evident, and disturbing, when flipping pages: in Okular, PgDn can take a full second, while in KPDF page flipping looks instantaneous.

Tested on a 1.8GHz Pentium M machine running Fedora 8. KPDF is Fedora's 0.5.8 RPM and Okular is SVN built against Fedora's kdelibs4 4.0.1-6.fc8 RPM. Both use the same Fedora 8 libraries except for kde3 vs. kde4.

The performance gap seems to depend on the document. Here's a random PDF showing the issue: <http://law.wustl.edu/WULR/84-5/hurtyin.pdf>.

I have Okular configured with "Aggressive" memory usage and background generation enabled, and I let it sit for a few seconds before pressing PgDn (to give it time to pre-render the next page), but the response is still often slow. The system is otherwise idle.

Notably, the PgDn rendering time in Okular isn't constant: it's sometimes very fast, and sometimes takes a full second. I'm unable to conclusively correlate this with anything, including the amount of time waited before pressing PgDn.

This might be relevant: when I press PgDn, okular immediately spews this to stderr:
okular(23524) Okular::Document::requestPixmaps: request id=3 663x948@5
okular(23524) Okular::DocumentPrivate::sendGeneratorRequest: sending request id=3 663x948@5 async == true
The actual display update happens about a second, and the CPU is at 100% inbetween.