Is a 12 MB/s microSD overkill for what the glamo driver does?
jimcolt at gmail.com
Thu Jul 31 15:07:50 CEST 2008
Oh, I see. Good thought about flushing cache.
The speeds for read and write are different on a SD card with read being
always faster and so I was thinking to do only the read test and to have
dd(1) read directly from the device rather than going through the file
system - taking the file system code out of the picture since time due to it
is a constant factor.
The size of the read buffer won't matter since what was read is given to
/dev/null. The speed and buffering of the underlying Glamo driver and SD
card will be the only player - which is what I am testing.
I'll use something like:
time dd if=/dev/mm<whatever the SD device name is> count=512000 bs=1024
..and dividing the value for System time into (512000 * 1024) for the
On Wed, Jul 30, 2008 at 11:07 PM, Mike Montour <mail at mmontour.net> wrote:
> Jim Colton wrote:
> > Hi Mike,
> > I looked at the code your wrote. It doesn't do anything that 'time dd'
> > already can do.
> It includes an fsync() in the timing measurement when writing the file,
> and does a posix_fadvise() before reading it back (both intended to make
> sure that the I/O is going to the device under test rather than just
> hitting cache memory). You can do the same things in a 'dd'-based test,
> but it requires a few additional steps.
> support mailing list
> support at lists.openmoko.org
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