[PATCH 2/2] exa/mixed: Exclude frontbuffer from deferred pixmap handling.

[Maarten Maathuis]

2010/12/10 Michel Dänzer <michel at daenzer.net>:
> On Don, 2010-12-09 at 21:17 +0100, Maarten Maathuis wrote:
>> - Apps like xterm can trigger a lot of fallback rendering.
>> - This can lead to (annoyingly) high latencies, because you
>>   have to wait for the block handler.
>
> Doesn't this decrease throughput of the xterm output though due to the
> higher migration overhead?
>
> Do you have a simple recipe for reproducing high latencies?

You need a driver that doesn't access the frontbuffer directly (NV50+
nouveau for example) and then just do dmesg a couple of times before
the last one is done. You'll notice that you can't even see some of
the text come by (try loading the cpu's to maximum to make the effect
stronger). I know this solution sacrifices throughput (no idea how
much). In the past i did get a few questions from people who were
using xterm or similar terminals (around the point were the default
was no longer to use wfb) about slowness, i checked it out and it
wasn't a throughput issue.



>
>
> --
> Earthling Michel Dänzer           |                http://www.vmware.com
> Libre software enthusiast         |          Debian, X and DRI developer
>



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