Bug#583653: xserver-xorg-video-radeon: 15x-slower performance regression in KMS mode for 2D operations

[Sylvain Beucler]

On Sat, May 29, 2010 at 04:21:46PM +0200, Michel Dänzer wrote:
> On Sam, 2010-05-29 at 15:02 +0200, Sylvain Beucler wrote: 
> > On Sat, May 29, 2010 at 01:05:36PM +0200, Michel Dänzer wrote:
> > > On Sam, 2010-05-29 at 10:21 +0200, Sylvain Beucler wrote: 
> > > > 
> > > > The attached simple test runs at 17FPS in KMS mode on my computer,
> > > > against 300FPS in non-KMS mode.
> > > 
> > > Forgot to mention: sysprof or oprofile profiles of slow and fast runs
> > > might be interesting, at least if the CPU is pegged during the runs.
> > 
> > Here are 2 sysprof runs:
> > - UMS / fast:
> >   - kernel 11.25%
> >   - X 77.20%
> > - KMS / slow:
> >   - kernel 90.28%
> >   - X 5.79%
> 
> Unfortunately, there's no information about where in the kernel the
> cycles are burnt. This information should be available with sysprof
> 1.1.x and a kernel with the performance counter/event framework.

Quite a nice tool:

__libc_start_main                                              0,00%  93,67%
  _start                                                       0,02%  87,66%
    In file /usr/bin/Xorg                                      0,13%  87,64%
      In file /usr/lib/xorg/modules/libexa.so                  0,04%  86,60%
        In file /usr/lib/xorg/modules/drivers/radeon_drv.so    0,08%  86,48%
          radeon_bo_open                                       0,00%  79,87%
            In file /usr/lib/libdrm_radeon.so.1.0.0            0,00%  79,87%
              drmCommandWriteRead                              0,00%  79,86%
                __kernel_vsyscall                              0,00%  79,86%
                  - - kernel - -                               0,00%  79,86%
                    on_each_cpu                               36,81%  36,81%
                    __purge_vmap_area_lazy                    20,31%  20,31%
                    flush_all_zero_pkmaps                      7,84%   7,84%
                    vm_unmap_aliases                           1,65%   1,65%

What do you think that means?


> Anyway, this probably means it's an issue in the kernel, not the X
> driver. May be solved already in newer kernels, there have been some AGP
> performance improvements which I'm not sure have made it into Debian's
> 2.6.32 DRM backport.

-- 
Sylvain