Slow switching between dives?

[Linus Torvalds]

Ho humm. I haven't actually bisected this or anything, but I'm hoping
somebody else noticed and might have picked up on when this started..

I've got a fast CPU, but switching dives isn't "instant". You can
particularly tell when just scrolling down the dive list using the
cursor keys. It's not *slow*, but it sure isn't fast.

We used to have this situation where the deco processing took up a lot
of time, but that doesn't seem to be it. Yes, "add_segment()" is
fairly high in the profiles at 11% of CPU time, and "factor()" is
another 4% or so, but that's pretty much it. Most of the time seems to
be GUI costs.

The top entry in a profile of me scrolling down the list is

  12.55%  qt_qimageScaleAARGBA_down_xy_sse4<false>

but there's some truetype code at 3% and a lot of libQt5Gui stuff in
the ~1% range.

I *thought* we used to update the dive profile asynchronously so that
you could step down the dive log without waiting for the profile to
render all the time. Has that code bit-rotted perhaps?

Or is it just me?

             Linus