Performance problems with emacs-X11 in current cygwin

[Ken Brown]

On 6/8/2012 12:45 PM, Ken Brown wrote:
> On 6/8/2012 11:33 AM, Achim Gratz wrote:
>> Ken Brown writes:
>>> As I said earlier, I don't understand very well how git branches work,
>>> but I *think* this means we have to look in the 2-32 branch, prior to
>>> the 2.31.0 tag, to find the problematic commit. I've checked out the
>>> 2-32 branch, and I guess the next step is to find a problem-free
>>> revision of that branch, and then bisect between it and the 2.31.0
>>> tag. I'm in the process of reading the git documentation to figure out
>>> how to do that, but I wouldn't object if someone would save me some
>>> time by giving me the appropriate git commands.
>>
>> I've had a quick look at how the GNOME folks use their release branches:
>> they are tagged in master and then only some version bumping and a few
>> quickfixes. There are no odd numbered releases, so I assume they start
>> the disruptive changes right after a release, tag the unstable version
>> in master with an odd number and then work out the kinks until the new
>> release is done.
>>
>> So, you can indeed start on the 2.32 branch and then bisect down to the
>> 2.30 tag. Don't bother with the run-up between 2.31 and 2.32, just
>> bisect it whole, the bisect sequence will be just one build longer if at
>> all.
>>
>> git checkout glib-2-32
>> git bisect start bad
>> git bisect good 2.30.3
>>
>> If any of the intermediate versions doesn't build, say
>>
>> git bisect skip
>>
>> with the offending commit still checked out.
>
> Thanks, Achim. That helps a lot. The only thing I might have to change
> is the starting point for the bisection, since the tag 2.30.3 represents
> a fairly recent commit. But I think starting with 2.30.1 should work.
> I'll give it a try.

The bisection shows that the first problematic commit is this one:

http://git.gnome.org/browse/glib/commit/?h=glib-2-32&id=7eae486179e2799c369ed9ffcea663bf9161ce79

Author: Ryan Lortie <desrt@desrt.ca>
Date:   Wed Aug 31 22:07:02 2011 -0400

     GMain: simplify logic for g_wakeup_acknowledge()

     Instead of messing around with context->poll_waiting, just look at 
the GPollFD to see if the GWakeup needs to be acknowledged.

In case anyone else wants to confirm this, you can get my glib builds by 
running

   setup.exe -K http://sanibeltranquility.com/cygwin/kbrown.gpg

and adding http://sanibeltranquility.com/cygwin to the list of mirrors. 
  The problematic version is

   libglib2.0_0-2.30.90_7eae4861-1

and the preceding version (without the problem) is

   libglib2.0_0-2.30.90_87880df-1

I've tested the latter with emacs-23, emacs-24, and gvim.

Ken

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