very high memory usage in -current

Some time (probably some months) ago I occasionally noticed very high memory 
usage on my CURRENT notebook. I don't think this has always been the case, 
but I'm not 100% sure.

For me, this is reproducable very easily if I view some large (3000x2000 
pixels) .jpg files in konqueror.

On my 6.2 system, memory usage goes up quite a bit while decoding the image, 
then it drops a bit. If I close the image, memory usage is normal again.

On my current system, sometimes memory usage goes up very high when opening an 
image and doesn't go back to normal, even if I close the image. It only goes 
back to normal if I close konqueror.

Note that I see this also with a gtk app, so this is not a KDE bug. Also, at 
least in konqueror, I can reproduce this with .png files, so it's also not a 
jpeg library bug. CURRENT and ports on both systems are up to date.

I don't really know what's causing this problem. Maybe it's related to 
jemalloc, but I'd be surprised if no one else has noticed this before.

size/res values reported by top

6.2 desktop pc with nvidia binary driver
konqueror 40M/30M

CURRENT notebook with the i810 driver
konqueror 290M/250M

Any clues or more information needed?

Thanks,
Stefan