13.2.1 for XO-1 using external SD card slot

[James Cameron]

On Fri, Jun 20, 2014 at 09:39:32AM +1000, James Cameron wrote:
> Therefore using an SD card instead of NAND flash should increase I/O
> performance, decrease processor time, and increase available memory.

I've measured the increase in available memory.

With the laptop freshly booted at the activity view and the journal
icon coloured, a program is run that consumes memory in order to
determine how much is available;

- moving the root filesystem from NAND to SDIO is a 7% gain, from 146
  MB to 156 MB,

- leaving the root filesystem on NAND and adding 64 MB swap on SDIO is
  a 31% gain, from 146 MB to 191 MB,

- moving the root filesystem from NAND to SDIO and adding 64 MB swap
  on SDIO is a 41% gain, from 146 MB to 206 MB.

A visualisation of the results:

https://plot.ly/~quozl/7/xo-1-256-mb-usable-memory-1321-nand-vs-sdio-as-root/

The test program:

http://dev.laptop.org/~quozl/z/1WyA0M.txt (oom.c)

Measurement was the anon-rss in the kernel OOM message, e.g.

[  761.307460] Killed process 937 (oom) total-vm:197692kB, anon-rss:183048kB, file-rss:4kB

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