Comment 128 for bug 311895

On Wed, 3 Jun 2009 00:06:45 -0700 (PDT)
<email address hidden> wrote:
> as we discussed last week in Barcelona, I have now tried -intel git
> head, mesa git head, 2.6.30rc7 on my home system with the external
> monitor again, now with the extra 1 GB of RAM that I plugged in last
> week.
>
> As you suspected, the underruns are now gone, apparently having a
> second RAM bar now provides enough bandwidth for the graphics card to
> avoid underruns.
>
> I'm happy to test further patches, I can easily remove the extra GB
> of RAM again. The very same symptom happens on the Samsung NC10 of a
> friend of mine, I can test stuff on his machine as well (with some
> delay).
>
> My impression is that with FB compresssion my machine is simply not
> fast enough, regardless of the watermark settings (given that all of
> above patches failed consistently). Would it be possible for the
> driver to disable FB compression dynamically if it encounters pipe
> underruns, such as "twice in five minutes"?
>
> I wonder why this problem didn't occur at all with earlier driver
> versions (2.4). Didn't that use FB compression yet?

Great, thanks for the update. Yes, we should detect either memory
configuration or underruns and take appropriate action. Previous
drivers didn't modify the FIFO or DSPARB settings, so the defaults may
have been working on your platform, or something else changed to affect
the way we access memory (it's also possible that FBC was disabled on
older releases in your config for some reason).

Jesse