Wine Traffic #85 For 5 Mar 2001

We've recently been working on getting American McGee's Alice (a visually stunning game, if you haven't seen it before) running well under Wine, and we've run into a serious speed issue with synchronization objects like Mutexes.

Currently, Alice runs at about 50% the framerate it gets in Windows with the same graphics driver (NVidia). When we started investigating, it turned out that the reason for this is that it's spending half of it's time in the WineServer. At first we assumed that this was due to the fact that the GL thunks need to grab the X11 lock. We realized that this wasn't necessary for most GL calls if we're using a direct rendering GL implementation, and turned off the locks. There was no effect - because there really wasn't much contention for the x11 lock.

After going through a number of similar Wine internal possibilities and getting nowhere, we finally realized that the problem was the app itself. It's grabbing and releasing a mutex of it's own bazillions of times each frame. Since there's nothing much we can do about that we started thinking about the proposed linux kernel module approach. After re-reading the thread (EdNote: you call also look at WWN coverage part #1 and BROKEN KCREF) and looking over the prototype, I have to concur with Alexandre's judgement - the prototype that exists is trying to do too much work.

I don't see how you are going to make this work reliably. A basic design principle of the server is that no matter what a client process does, it cannot break either the server or other clients; given the number of bugs Windows apps contain, I feel this is very important.

As soon as you introduce a shared memory area, you need the collaboration of all clients to ensure the stability of the whole system, since any client can corrupt system data structures. This is very bad. Also since the server is single-threaded its data structures don't need to be protected; but as soon as you manipulate them from multiple threads you need locking mechanisms, which will probably cost a lot in performance too.

Product	Overall rank (1..10)	The good	The bad	The bottom line
VMware Workstation 2.03	9	Provides a self-contained Windows environment that makes its Linux host platform nearly immune to collateral damage.	It's expensive.	VMware is an essential IS tool for multiplatform application management.
NeTraverse Win4Lin 2.0	7	Simple installation; good documentation; works as promised.	No DirectX or Windows networking support.	Win4Lin is a bargain Windows emulation platform if you need just the basics.
Wine	5	Runs Windows apps without Windows; strong user community	Difficult to use; spotty application support; still under heavy development.	With its innovative approach to Windows compatibility, Wine is destined to play a major role in the world of Linux. But for now, it's not quite ready for prime time.

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