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 of=/dev/null ..and dividing the value for System time into (512000 * 1024) for the result. On Wed, Jul 30, 2008 at 11:07 PM, Mike Montour <[EMAIL PROTECTED]> 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@lists.openmoko.org > https://lists.openmoko.org/mailman/listinfo/support >
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