Re: [Qemu-devel] [patch] cocoa.m - Core Graphics support

[Anthony Liguori <anthony@codemonkey.ws>]

Mike Kronenberg wrote:
> While testing with Quartzdebug, I realized, that qemu is updating 
> always the whole screenwidth even if only the mouse is moved... is 
> this a qemu problem, or is this the default windows behaviour?

VGA framebuffer operations come in as memory operations.  They're 
tracked by watching what memory gets dirtied.  This can only operate at 
a page-granularity so this results in scan-line granularity updates.  
The VNC front-end goes to great lengths to keep a shadowed framebuffer 
and reduce these updates to a smaller update region.  You could possibly 
look at refactoring that code.  However...

I would be amazed if screen updates on OS X are so slow that it would 
make a difference if updates are in scanline granularities.  The copying 
latency is nothing compared to the other latencies in QEMU.  A modern 
processor can move memory at an extremely high speed.

At a refresh rate of 30 times per second, this is only ~4MB of data for 
mouse movements.  A typical processor can easily handle many GB of data 
per second.

Regards,

Anthony Liguori

> Mike
>
> [1] 
> http://developer.apple.com/documentation/Carbon/Conceptual/QuickDrawToQuartz2D/tq_image_data/chapter_6_section_2.html#//apple_ref/doc/uid/TP40001098-CH227-BBCFFDBB