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List:       kwin
Subject:    Re: List of gfx cards and how they work with KWin
From:       "Lucas Murray" <lmurray () undefinedfire ! com>
Date:       2008-09-18 17:55:45
Message-ID: f09827650809181055r3f9024eck5a93ac86db531507 () mail ! gmail ! com
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On Fri, Sep 19, 2008 at 1:29 AM, Lubos Lunak <l.lunak@suse.cz> wrote:
> On Thursday 18 of September 2008, Rivo Laks wrote:
>> Ühel kenal päeval (neljapäev 18 september 2008) kirjutas Lubos Lunak:
>> >  Also, looking at the list, it appears quite obvious that there is no
>> > simple rule for selecting which cards should or should not have
>> > compositing enabled by default (for example, GeForce4 4200 Go outperforms
>> > GeForce 6200 by quite a lot in glxgears, and regardless of how bad
>> > benchmark glxgears is, this should mean something). So, I'm open to
>> > suggestions and good ideas about how we could handle this :).
>>
>> Not suprising actually. 6200 is a low-end card (as are e.g. 5200 and 7300),
>> but 4200 is a mid-end one (in GeForce4 series, 4 digit numbers meant
>> mid/high end cards and 3 digit ones were low end cards).
>
>  Hmm ... might explain why the 6200 is fine with passive cooling :).
>
>> For NVidia's GeForce 5-9 series, it might be possible to determine the
>> card's speed by looking at the first two digits of the model number. Low
>> end cards have 2nd digit lower than 5, so one possibility would be to
>> enable compositing if
>>   model[1] >= '5' || model[0] >= '7'
>> (this assumes that for GeForce7 and up, even low-end cards are powerful
>> enough. Not sure if that's the case).
>
>  Actually all the GeForce cards I have are quite fine. Even the GeForce2 one
> is acceptable. I guess this all really depends on the user and their
> perception of the performance. I'm currently thinking about enabling it
> automatically for any ati/intel/nvidia card that has acceleration working
> (like we already do in CompositingPrefs).
>
>> And in some cases, you might even want to look at card model/driver combo.
>> E.g. my GeForce 9600 was slow as hell until I discovered some hidden
>> settings (which are also listed somewhere at techbase). After changing
>> those settings manually, everything works very fast. But I don't know when
>> those "good values" will be the defaults...
>
>  I'm afraid those are next to impossible to detect from KWin :-/. There is now
> also a check for detecting too bad performance, but that one just checks for
> three consecutive repaints taking more than 1 second, which can catch only
> really pathetic cases. And I have no idea how to detect just bad performance
> without occassionally triggering also when there will be only a higher system
> load.

Keep a running five second average, if the framerate over the last
five seconds is less than say 15-20fps bring up a dialog suggesting
the user to disable compositing. This dialog would also have a "ignore
future performance" that will prevent it from ever displaying again
for the user. If it's also possible to check CPU usage and whatever
when the framerate is low maybe prevent the dialog from showing if
usage is over 75% (No need to poll often, just every five seconds
while the performance is bad)? It won't detect other bottlenecks but
it's one less to worry about.
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