larsi@gnus.org (Lars Magne Ingebrigtsen) writes:

> There are now three things that take about the same time when entering
> a group, and account for 95% of the time spent:
>
> 1) parsing NOV headers (this has gotten slower due to MIME stuff, I'm
>    guessing)
> 2) scoring
> 3) creating and outputting the threads
>
> If someone wants to look closer at this, then I'm all for it.  :-)

Here's a small tweak, which speeds up threading a bit (around 5-10%):
`gnus-parent-id' is usually called without the optional argument -- in
that case we only want the last msg.id in References, so we don't really
need to call `gnus-split-references' to parse *all* the references and
build a list of them.