[Sugar-devel] XO-1 vs Sugar 0.104 performance, and swap to NAND Flash

[James Cameron]

What benefit is an SD card on an XO-1?

My tests of about 400 starts show some benefit of using an SD card, on
activity startup time.  The benefits are:

- boot time was decreased by several seconds; because of reduced
  demand for memory,

- first activity start after boot was decreased by several seconds;
  because of reduced demand for memory,

- when there is no contention for memory, mean cold activity startup
  time is decreased by between 1 and 2 seconds; because of both
  different data rates and no decompression, and;

- writing journal entries is slightly faster.

There was no benefit on activity startup time where caches were warm;
everything needed by the activity was already in memory, so there was
no extra wait.

The SD card was a SanDisk Ultra 8GB, class 10, 30 MB/s.  Sequential
read speed on a modern desktop is 18.5 MB/s.  But on the XO-1 the
speed is 6.3 MB/s.  There may be little advantage to using a faster
card.

For Sugar 0.104 comparing results by activity, between NAND flash and
SD card:

                        bundle_id    cold    warm    std  ratio  tests

             com.garycmartin.Moon  11.928  10.294  0.492  0.863  24
             com.garycmartin.Moon  11.809  10.585  0.516  0.896  24  sd
       com.jotaro.ImplodeActivity   9.084   9.017  0.498  0.993  24
       com.jotaro.ImplodeActivity   9.560   8.904  0.501  0.931  24  sd
       org.laptop.AbiWordActivity  20.868  16.862  0.376  0.808  24
       org.laptop.AbiWordActivity  19.326  16.441  0.277  0.851  24  sd
       org.laptop.AcousticMeasure  12.330  10.513  0.137  0.853  24
       org.laptop.AcousticMeasure  11.854  10.552  0.254  0.890  24  sd
             org.laptop.Calculate  11.591   9.920  0.120  0.856  24
             org.laptop.Calculate  12.152   9.975  0.205  0.821  24  sd
          org.laptop.HelpActivity  14.654   8.981  0.329  0.613  24
          org.laptop.HelpActivity  13.025   9.027  0.345  0.693  24  sd
       org.laptop.MeasureActivity  16.381  11.364  0.135  0.694  24
       org.laptop.MeasureActivity  15.000  11.634  0.344  0.776  24  sd
              org.laptop.Memorize  17.961  14.550  0.183  0.810  24
              org.laptop.Memorize  16.442  14.724  0.240  0.896  24  sd
               org.laptop.Oficina  12.231  12.029  0.351  0.983  24
               org.laptop.Oficina  13.250  12.270  0.585  0.926  24  sd
                 org.laptop.Pippy   8.752   8.202  0.128  0.937  24
                 org.laptop.Pippy   9.897   8.404  0.467  0.849  24  sd
        org.laptop.RecordActivity  16.956  12.652  0.145  0.746  24
        org.laptop.RecordActivity  15.341  12.501  0.255  0.815  24  sd
         org.laptop.sugar.Jukebox   9.666   8.986  0.108  0.930  24
         org.laptop.sugar.Jukebox   9.821   9.287  0.472  0.946  24  sd
    org.laptop.sugar.ReadActivity  11.296  10.477  0.165  0.928  24
    org.laptop.sugar.ReadActivity  11.080  10.618  0.463  0.958  24  sd
            org.laptop.TamTamMini  18.628  14.734  0.576  0.791  24
            org.laptop.TamTamMini  19.838  14.615  0.288  0.737  24  sd
           org.laptop.WebActivity  19.425  12.527  0.217  0.645  24
           org.laptop.WebActivity  17.935  12.937  0.274  0.721  24  sd
                 tv.alterna.Clock  10.061   7.124  0.123  0.708  24
                 tv.alterna.Clock  21.226   7.522  0.316  0.354  24  sd ?
                 vu.lux.olpc.Maze   8.366   8.265  0.120  0.988  24
                 vu.lux.olpc.Maze   8.998   8.646  0.370  0.961  24  sd
                vu.lux.olpc.Speak  24.555  12.075  0.208  0.492  24     ?
                vu.lux.olpc.Speak  16.526  11.946  0.358  0.723  24  sd

The cold results for Clock and Speak are unexpected, but this may be
related to gst-plugin-scan.

(Reference: test #6, vs #10)

-- 
James Cameron
http://quozl.linux.org.au/