[Bug 12689] New: Input messages lingering in server slowing down wine

http://bugs.winehq.org/show_bug.cgi?id=12689

Summary: Input messages lingering in server slowing down wine
           Product: Wine
           Version: CVS/GIT
          Platform: Other
        OS/Version: other
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

Created an attachment (id=12347)
 --> (http://bugs.winehq.org/attachment.cgi?id=12347)
testcase for problem

Attached testcase illustrates the problem. The problem was originally found in
a fan-developed Forsaken mod. I couldn't get feedback on this on wine-devel, so
I'm opening a bug for this. Close if it's not a bug or is non-fixable.

How to reproduce: hold a key and move mouse over the window, preferably also
clicking mouse buttons, main loop latency steadily increases from 10 to 50 (and
even 100) in a short time. In a game this means going from 100 fps to 20 or 10
just because of input messages. Has to be noted that in the actual game the
rate of slowdown seemed at least 2-3 times faster when just holding one key and
moving mouse, for reasons I don't know, but the testcase still should enough to
show the problem.

What the testcase is doing is bad practice, it's basically refusing to process
certain types of messages, and PeekMessage just once during a loop is probably
bad as well, but that's what the game was originally doing in its main game
loop. There are several concerns about it:

1) No slowdown happens on Windows, either in game or in this testcase. No
matter how much I move the mouse holding key and clicking madly, it shows same
stable 15-16 ticks latency in the testcase. I don't know what it does, but
somehow it handles this situation better than Wine.

2) Can this (broken) way of doing things be exposing some inefficiency in
message handling, maybe something that could use optimization? I tried to put
debug hacks into queue_hardware_message(), it seems that when slowdown is
already VERY bad in Forsaken (10fps), message queue in wine server has about
400 or maybe 600 messages. Is that kind of processing overhead per message
inevitable? (This is happening on AMD Athlon(tm) 3200+). Perhaps somebody who
knows that part of code well may be interested in looking into performance
issues in this case. Because, if 400-600 messages in the queue slow down the
application to a crawl, then who knows, perhaps it decreases performance of
more well-behaved but input-intensive apps as well, just less drastically
(holding one or several keys to move, all the while aiming with mouse and
abusing mouse buttons is a common thing in games, so there can be quite a few
input messages flooding the server).