[Spice-devel] "qxl: add optinal 64bit vram bar" patch significantly slows down Spice

[Gerd Hoffmann]

On 04/06/12 15:54, Hans de Goede wrote:
> Hi Gerd,
> 
> While cherry picking some spice patches into my own qemu-kvm-1.0 branch,
> so that we can add them to Fedora-17 I noticed a significant slowdown
> after I was done cherry picking. Investigation has shown your
> "qxl: add optinal 64bit vram bar" patch to be the culprit.
> 
> I noticed this using an old Fedora-14 32 bits vm with an xorg-x11-drv-qxl
> patched to use the async methods.
> 
> If I scroll through the gnome applications menu with the mouse with
> plain qemu-kvm-1.0 all is fine, but once I add your:
> "qxl: add optinal 64bit vram bar" the updating of the display
> becomes noticably slower, the blue bar highlighting the selected
> menu entry becomes lagged compared to the mouse cursor.

Avi?  This looks like a memory aliasing issue.

Old state:
  vram bar, backed by memory

New state:
  vram bar, 64bit, backed by memory, might not be mapped.
  vram bar, 32bit, alias for the first part of the 64bit bar.

Full patch:

http://git.qemu.org/?p=qemu.git;a=commitdiff;h=6f2b175a090f367c3aab2226c4741b439671307a

Any hints?

cheers,
  Gerd