Hello,

I rewrote the part responsible for agenda generation in "org-agenda.el".
Basically, I refactored some hot loops and introduced a cache mechanism
for data extracted out of agenda files.

I expect to see some interesting improvements when viewing the agenda
with a span larger than one day, or when generating an agenda view
without having touched most of the agenda files since last view.

Some feedback about the new agenda speed would be nice.

Also, I certainly broke a few things along the way. Please report
anything suspicious.

The only thing that is expected to be defective is
`org-agenda-include-inactive-timestamps'. It has no effect at the
moment. I can activate it again, but I'm wondering if it's worth the
overhead. It is already possible to display clocks and closed timestamps
in the agenda. Other inactive timestamps could be ignored from the
agenda altogether. This is their sole purpose, after all. WDYT?

I attach the behemoth patch here for quick testing. Further bug fixes
will happen in "wip-agenda-speedup" branch.

Regards,

-- 
Nicolas Goaziou                                                0x80A93738