https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244356

--- Comment #52 from Olivier Certner <olivier.free...@free.fr> ---
(In reply to Maurizio from comment #48)

Thanks Maurizio. I have roughly the same output as yours with my KT_32G
(Kingston DataTraveler 100 G3, showing up as <Kingston DataTraveler 3.0> in
kernel logs), *provided* that I set I/O size to anything but "Random" (I need
to investigate this).

In this case, the read speed reported by `usbtest` happens to be fairly stable
at 110MiB/s, whereas write speed is quite bumpy and ranges from 5 to 40MiB/s.
To me, it seems that your trace essentially shows the same performance profile.
The write speed in particular is not a lightning one, but could be considered
acceptable.

What is very strange, however, is that an `iostat` recording of a `dd` to exFAT
shows that transfer again proceeds at decent speeds during ~2s, and then stalls
for ~2s, and the pattern goes on and on. And I observe this on Linux and MacOSX
as well.

Hans, do you consider this pattern as normal? I never observed such one with
USB 2.0 sticks so far.

Maurizio, if you have time, could you try the `dd` (with, e.g., parameters
`if=/dev/zero of=<file_on_stick> bs=1M count=1024`) test above and capture the
output of `iostat -w 1 <stick_device>` during the test?

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