CPU hogging in the current master

[Linus Torvalds]

On Thu, Sep 26, 2013 at 1:30 AM, Lubomir I. Ivanov <neolit123 at gmail.com> wrote:
>
> i have tested both patches (from linus and robert) and the performance
> is similar. it still takes near a second to when simply navigate
> trough the test case dives with the arrow keys. to confirm again that
> calculate_deco_information() is the cause i have put a "return;" in
> the function making it a NOP, which makes the UI response snappier. if
> i also go in and disable the marble globe update for example it's even
> better but not that significantly as a side-by-side comparison to the
> TTS NOP factor.

Yes. I'll do some more work. On my machine it is now basically
instantaneous, but that's a pretty beefy one. I think I can use
profiling to see what can be improved without having the instant
feedback (it used to be slow even on my desktop)

That said, I think this only hits cases like that particular dive: two
deep dives where we do into deco and surface before we've gotten out
of it. And top it off with just half an hour of surface interval
between the two. So the TTS calculations get a bit crazy.

I think this special case is actually solvable by just limiting the
TTS calculation to the length of the dive. I wanted to get rid of the
extreme sillyness before (it used to spend 50% of the time in just
calculating "pow()", now that's gone.

             Linus