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Date:	Wed, 13 Jun 2012 17:07:17 -0400
From:	Ken Brown <kbrown AT cornell DOT edu>
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Subject:	Re: Performance problems with emacs-X11 in current cygwin
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On 6/13/2012 2:40 PM, Ken Brown wrote:
> On 6/10/2012 8:45 PM, Ken Brown wrote:
>> 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 AT desrt DOT 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.
>
> I think this commit contains a typo: "events" should be "revents".
> (context->wake_up_rec.events is always nonzero at this point in the
> code, so it makes no sense to test that.) As a result,
> g_wakeup_acknowledge() is being called much more often than necessary. I
> think this could easily explain the performance problems that have been
> reported, but I won't have a chance to test this on my (slow) XP system
> for a while, and possibly not until tomorrow.

I've confirmed that fixing the typo solves the problem on my XP system. 
  I suspect that this issue is not specific to XP after all and has more 
to do with the slowness of the machine, so that the performance problem 
is more noticeable.  In any case, it's clearly a glib bug.

I've filed a bug report upstream:

   https://bugzilla.gnome.org/show_bug.cgi?id=678052

Ken




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