Dear Lionel,
Thanks for your reply. Please see my reply inline.
Thanks & Regards,
Lindo Lonappan.
Lionel Landwerlin wrote:
On Mon, Nov 30, 2009 at 11:40 AM, Lindo Lonappan <li...@tataelxsi.co.in> wrote:
Dear all,
We are using IDirectFBSurface::Blit() call for surface rotation.
Our hardware doesn't support surface rotation. We are using the software
fall back provided by DFB-1.4.2 for this.
We observe that surface rotation is faster if we create surface in the
system memory. There is an extra time of 200ms for rotation if we create
surface in video memory.
But since we have hardware fall back for other operations we need to use the
video memory. They will have better performance in video memory.
1. why the rotation in system memory faster than video memory?
Probably because video memory is mapped uncached (that's usely the case
with frame buffers).
I don't get this reply exactly. I am not very good in device driver
part. Can you please explain this?
2. We guess in the case of video memory there is some overhead of switching
between kernel and user space since we are using a software fall back for
rotation. Is this is correct?
There is no switch kernel/user when using the software fallback.
Thanks for correcting me.
3. Is there any way of creating surface which will not have any performance
difference in both hardware and software fall back?
(ie We need to create a surface which will give a performance of system
memory for surface rotation and a performance of video memory for operations
supported by our hardware.)
You will have to use cached mapping for your buffers and correctly manage cache
synchronization in your gfxdriver.
Thanks for the reply. One more question is the pointer returned by
Lock() is memory mapped ? Question is because even if i tried to rotate(
or mirror image) the surface with some algorithm(which requires memory
copy) there is also a performance difference for system memory surface
and video memory surface. In that case also system memory have the
better performance.
Thanks a lot in advance!!!
Good luck.
--
Thanks & Regards,
Lindo Lonappan.
--
Lionel Landwerlin
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