[dev] dwm does something bad to X.org 1.7.6

Hello,

Debian testing has replaced Xorg 1.7.5 with 1.7.6 about 3 days ago.
Because i had not logged out of my X session in between, i picked up the
new X server only today.

dwm does something very wrong to it, causing it to consume a lot of cpu
(say 25-50% according to top with 3s interval) and making X clients
sluggish to unusable.

I would not bet my life that the effect was not there with 1.7.5, but
I had noticed nothing at all, I mean it's only today that firefox got
very more sluggish than usual.

Experimental evidence:
- It is clearly dwm and not another client: the effect is there even when
no other clients run but a lame xterm with top or ps inside.
- It happens not only with my personal build and patches, but with just
about every revision, from tag 0.1 to pristine tip.
- I disabled the debug traces we get in the latest revisions from hg, to
no avail (btw. thanks for nothing for leaving that on, i had not noticed
how huge my .xsession-errors had grown)
- It does not happen with any other WM i had on hand (icewm, twm, olvwm,
mwm)

At this point I don't know if it has anything to do with the graphics
driver (intel in X, i915 in kernel) as I have only my laptop at hand. I
shall try on my server later tonight.
Don't know if that has anything to do either, but with the most recent
2.6.32 kernel in debian testing, I had to disable kernel mode setting in
i915 as it was a cause of memory corruption after resume from disk.
Because I did not bother to reenable a vga= argument in Grub, I have
been running consoles in real text mode for the last few weeks. Oh, and
X.org locks up the display from time to time when switching between X
and consoles, anyway.

At any rate there is no clear indication that there is a new frank bug
in X.org, rather there must be something that dwm does or quite possibly
does not do (wrt. other WMs) on the X wire, that keeps X.org busy. At
least, the X.org folks say that when the X server eats a lot of cpu
time, it's not necessarily an indication of an X.org bug (Uriel, *shut
up*) but rather that some X clients bomb the server with more or less
appropriate requests. What's for sure is that I am not embarking on a
gdb/profiling session of the X.org process on my own - but advice and
procedures are welcome.

I will also try another bunch of tiling WMs among those readily
available in debian testing, including dwm derivatives. We'll see who
triggers the "bug".

In the meantime i have no other option but to revert to icewm, my
former favorite, and, man, does it suck compared with dwm...
Please help me bring the arch-WM back to its senses !!! ;-)

Cheers

-- 
Benoit Triquet <benoit.triquet at gmail.com>
 .''`.
: :' :      We are debian.org. Lower your prices, surrender your code.
`. `'       We will add your hardware and software distinctiveness to
  `-        our own. Resistance is futile.