Messages in this thread | | | From | Miquel Raynal <> | Subject | Re: [PATCH] mtd: tests: Fix eraseblock read speed miscalculation for lower partition sizes | Date | Mon, 14 Mar 2022 16:59:55 +0100 |
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On Tue, 2022-02-08 at 10:39:05 UTC, Amit Kumar Mahapatra wrote: > While calculating speed during mtd_speedtest, the time interval > (i.e., start - finish) is rounded off to the nearest milliseconds by > ignoring the fractional part. This leads to miscalculation of speed. > The miscalculation is more visible while running speed test on small > partition sizes(i.e., when partition size is equal to eraseblock size or > twice the eraseblock size) at higher spi frequencies. > > For e.g., while calculating eraseblock read speed for a mtd partition with > size equal to the eraseblock size(i.e., 64KiB) the eraseblock read time > interval comes out to be 966490 nanosecond. This is then converted to > millisecond(i.e., 0.966 msec.). The integer part (i.e., 0 msec) of the > value is considered and the fractional part (i.e., 0.966) is ignored,for > calculating the eraseblock read speed. So the reported eraseblock read > speed is 0 KiB/s, which is incorrect. > > There are two approaches to fix this issue. > > First approach will be to keep the time interval in millisecond. and round > up the integer value, with this approach the 0.966msec time interval in the > above example will be rounded up to 1msec and this value is used for > calculating the speed. Downside of this approach is that the reported speed > is still not accurate. > > Second approach will be to convert the time interval to microseconds > instead of milliseconds, with this approach the 966490 nanosecond time > interval in the above example will be converted t0 966.490usec and this > value is used for calculating the speed. As compared to the current > implementation and the suggested First approach, this approach will report > a more accurate speed. Downside of this approach is that, in future if the > mtd size is too large then the u64 variable, that holds the number of > bytes, might overflow. > > In this patch we have gone with the second approach as this reports a more > accurate speed. With this approach the eraseblock read speed in the above > example comes out to be 132505 KiB/s when the spi clock is configured at > 150Mhz. > > Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com> > Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.
Miquel
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