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/
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