performance work

Jordan Crouse jordan at cosmicpenguin.net
Mon Dec 22 17:36:36 EST 2008


Greg Smith wrote:
> Hi Jordan,
> 
> Looks like we made a little more progress on graphics benchmarking. See 
> Neil's results below.
> 
> I updated the feature page with the test results so far:
> http://wiki.laptop.org/go/Feature_roadmap/General_UI_sluggishness
> 
> What's next?
> 
> Do we know enough now to target a particular section of the code for 
> optimization?
> 

I ran the raw data through a script, and came up with a nice little 
summary of where we stand.  My first general observation is that the 
numbers are skewed due to system activity - recall that X runs in user 
space, so it is subject to be preempted by the kernel.  I think that the 
obviously high numbers in many of the results are due to NAND or 
wireless interrupts (example):

6: 2261923 (5.25 ms)
7: 16690761 (38.73 ms)
8: 2306919 (5.35 ms)

You might want to re-acquire the numbers with wireless turned off and 
the system in a very quiet state.  If you want to be extra careful, you 
can run the benchmarks in an empty X server (no sugar) and save the 
results to a ramfs backed directory to avoid NAND.  You probably don't 
have to get _that_ extreme, but I don't want you to spend much time 
trying to investigate a path only to find out that the numbers are wrong 
due to a few writes().  In the results below, I tried to mitigate the 
damage somewhat by removing the highest and lowest value.

The list below is sorted by delta between accel and un-accel, with the 
"worse" tests on top (i.e - the ones where accel is actually hurting 
you) - these are good candidates to be looked at.  There are three 
reasons why unaccel would be faster then accel - 1) a bug in the accel 
code, 2) The accel path requires reading from video memory (which is 
very slow), and 3) the accel path doesn't punt to unaccel early enough.

The first two on the list (textpath-xlib and texturedtext-xlib) toss up 
a huge red flag - I am guessing we are probably seeing a bug in the driver.

All of the upsample and downsample entries are interesting, because the 
driver should be kicking back to the unaccelerated path - I'm guessing
that 3) might be in effect here - though 73 ms is a long time.

Most of the operations between 1ms and -1ms are probably going down the 
unaccelerated path.  Most everything in there probably should be 
unaccelerated, with the possible exception of the 'over' operations - 
those are the easiest for the GPU to accelerate and the most heavily 
used, so you probably want to take a look at those.

As before, I encourage you to investigate which operation are heavily 
used - if you don't use textured text very much, then optimizing it 
would be heavily on the geek points, but not very useful in the long haul.

Jordan
Test                                     Accel    Noaccel   Delta
------------------------------------------------------------------
textpath-xlib-textpath                   1562.60  1345.12  217.48
texturedtext-xlib-texturedtext           315.61   140.54   175.07
downsample-nearest-xlib-512x512-redsquar 106.37   33.25     73.12
downsample-bilinear-xlib-512x512-redsqua 96.57    35.22     61.35
downsample-bilinear-xlib-512x512-primros 83.36    34.81     48.56
downsample-nearest-xlib-512x512-lenna    78.18    29.83     48.35
downsample-bilinear-xlib-512x512-lenna   83.91    36.32     47.59
downsample-nearest-xlib-512x512-primrose 77.49    30.06     47.43
upsample-nearest-xlib-48x48-todo         86.23    60.14     26.09
upsample-bilinear-xlib-48x48-brokenlock  242.52   216.49    26.03
upsample-bilinear-xlib-48x48-script      237.69   211.70    25.98
upsample-bilinear-xlib-48x48-mail        234.40   208.43    25.97
upsample-bilinear-xlib-48x48-todo        239.85   213.94    25.91
upsample-nearest-xlib-48x48-script       81.67    57.02     24.65
upsample-nearest-xlib-48x48-mail         78.99    54.42     24.57
upsample-nearest-xlib-48x48-brokenlock   86.18    61.73     24.45
upsample-nearest-48x48-script            61.95    57.46      4.49
downsample-bilinear-512x512-redsquare    11.24    7.77       3.47
solidtext-xlib-solidtext                 11.70    9.51       2.19
textpath-textpath                        1081.14  1079.37    1.78
texturedtext-texturedtext                112.33   111.79     0.54
upsample-bilinear-48x48-todo             224.06   223.68     0.37
upsample-nearest-48x48-brokenlock        64.46    64.16      0.30
upsample-bilinear-48x48-brokenlock       226.51   226.25     0.26
downsample-nearest-512x512-redsquare     2.43     2.23       0.19
gradients-linear-gradients-linear        107.39   107.30     0.09
over-640x480-empty                       15.68    15.61      0.07
over-640x480-opaque                      20.19    20.12      0.07
add-640x480-opaque                       20.77    20.73      0.04
upsample-nearest-48x48-todo              60.75    60.71      0.04
add-640x480-transparentshapes            20.79    20.78      0.02
add-640x480-shapes                       20.76    20.74      0.02
multiple-clip-rectangles-multiple clip r 1.23     1.22       0.01
over-clipped-640x480-empty               0.95     0.94       0.01
over-640x480-text                        23.51    23.51      0.01
downsample-bilinear-512x512-primrose     7.08     7.08       0.00
multiple-clip-rectangles-xlib-multiple c 0.15     0.15       0.00
over-clipped-640x480-opaque              1.22     1.22       0.00
downsample-bilinear-512x512-lenna        7.03     7.04      -0.01
over-clipped-640x480-shapes              1.23     1.24      -0.01
downsample-nearest-512x512-primrose      2.03     2.05      -0.02
downsample-nearest-512x512-lenna         2.03     2.05      -0.02
over-640x480-transparentshapes           58.66    58.68     -0.02
over-640x480-shapes                      18.56    18.59     -0.03
upsample-nearest-48x48-mail              54.71    54.77     -0.07
add-640x480-text                         20.70    20.77     -0.08
solidtext-solidtext                      42.83    42.94     -0.10
add-640x480-empty                        20.66    20.80     -0.13
upsample-bilinear-48x48-mail             217.81   219.44    -1.63
over-clipped-xlib-640x480-opaque         4.55     6.26      -1.71
upsample-bilinear-48x48-script           220.89   222.80    -1.92
over-clipped-xlib-640x480-empty          3.67     6.04      -2.38
lines-lines                              426.79   429.16    -2.38
over-clipped-xlib-640x480-shapes         4.00     6.52      -2.51
curves-curves                            224.55   236.08   -11.53
over-xlib-640x480-empty                  29.88    48.30    -18.42
curves-xlib-curves                       245.46   264.19   -18.73
gradients-linear-xlib-gradients-linear   132.35   151.62   -19.26
over-xlib-640x480-opaque                 29.92    53.04    -23.12
add-xlib-640x480-transparentshapes       29.98    53.53    -23.54
add-xlib-640x480-opaque                  29.97    53.54    -23.57
add-xlib-640x480-empty                   29.93    53.61    -23.67
add-xlib-640x480-shapes                  30.05    53.77    -23.72
add-xlib-640x480-text                    29.75    53.59    -23.84
over-xlib-640x480-shapes                 29.77    54.93    -25.16
over-xlib-640x480-text                   29.83    57.75    -27.92
over-xlib-640x480-transparentshapes      29.76    91.67    -61.91
lines-xlib-lines                         275.59   481.84   -206.25









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