On Sunday 13 March 2011, Dirk Behme wrote:

Hi Arnd,

reading the flashbench README [1] what I really like is the explanation of the -a and the -O option. Explaining the options in this README, giving the examples and how to interpret the resulting figures really does help.

Somehow I miss something similar for the -s and -f options. I.e. how to select the proper values for --scatter-order and --scatter-span and how to interpret the output of -s and -f.

Once I understood it, I would be able to send a patch for the README ;)

Additionally, it would be nice to give the flashbench options used for the graphs [2] [3] in the LWN article. The LWN article explains quite nicely how to interpret the given graphs, but it's not mentioned which flashbench options were used to get these graphs.

Many thanks for your help and best regards

Dirk

[1] http://git.linaro.org/gitweb?p=people/arnd/flashbench.git%3Ba=blob%3Bf=READM...

Sorry for the late reply. I promise I'll get to it and update the README.

I should actually remove --scatter-order, it's too difficult to understand this. It specifies the log2 of the number of blocks in terms of --blocksize to be tested at the start of the medium. The output file can be interpreted by

gnuplot -p -e 'plot "output.file"'

or by importing it into a spreadsheet program like oocalc and using the XY chart function on two columns.

For --findfat, the output shows how each of the first N erase blocks on the drive reacts to certain access patterns within the erase block. Most drives do something different for a few blocks in the beginning to optimize storing the FAT on them. Each column is one erase block here. If they are all the same, the card does not have an optimzied FAT area.

Arnd