Checking new mail very slow with current CVS

[Russ Allbery <rra@stanford.edu>]

I just upgraded to the current CVS version of Gnus so that I could start
playing with nndiary, and I immediately noticed that checking new mail
with "g" is *much* slower than it was under 5.8.7.  Does anyone have any
idea what's changed and if there's anything I can do about it?  It's slow
enough to be fairly frustrating.

Here's the tail end of the message log; I've marked the two places where
there's a noticeable pause:

    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 22k
    nntp read: 23k
===>
    Reading active file via nnml...
    Opening nnml server...
    Opening nnml server...done
    nnml: Reading incoming mail from maildir...
    nnml: Reading incoming mail (no new mail)...done
    Reading active file via nnml...
    Reading active file via nnml...done
    Reading active file via nndiary...
    Reading active file via nndiary...
    Reading active file via nndiary...done
    Reading active file from sent via nnml...
    Opening nnml server on sent...
    Opening nnml server on sent...done
    Reading active file from sent via nnml...
    Reading active file from sent via nnml...done
    Checking new news...
===>
    Checking new news...done

The first pause isn't too bad, but the second pause is really noticeable,
and XEmacs does four or six garbage collection passes in the middle of
it.  Setting gnus-verbose-backends to 10 doesn't produce any additional
messages, and setting nnml-marks-is-evil to t makes no difference at all.

Setting gnus-debug-on-quit and pressing C-g in the middle of the long
pause gave the following backtrace:

Signaling: (quit)
  nnmail-group-pathname("work.watch.registry" "~/Mail/")
  nnml-possibly-change-directory("work.watch.registry" "")
  nnml-request-group("work.watch.registry" "" t)
  gnus-activate-group("nnml:work.watch.registry" nil t)
  gnus-get-unread-articles(nil)
  gnus-group-get-new-news(nil)
  call-interactively(gnus-group-get-new-news)

My *guess* from that is that for some reason activating every nnml group
is taking quite a long time and that 5.8.7 either didn't do that or did it
much more quickly.  I have several hundred nnml groups.

A search of the mailing list traffic reveals nothing except a few messages
about marks, which seems unrelated given that I see the same behavior
regardless of whether marks are enabled.

Does anyone have any ideas?

-- 
Russ Allbery (rra@stanford.edu)             <http://www.eyrie.org/~eagle/>