[Bug 244356] Writing to a USB 3.0 stick is very slow

[bugzilla-noreply at freebsd.org]

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

--- Comment #45 from Olivier Certner <olivier.freebsd at free.fr> ---
Hi Sébastien and Hans,

Contrary to what I recalled (or something changed since then), SD_64G and
SD_128G indeed seem bad. I did some tests in order to verify behavior on other
OSes, and both sticks exhibit the same transfer pattern on recent Linux and
MacOS X machines, i.e., usually 2 or 3s of decent bandwidth, followed by 2 or
3s without transfer and some "probe" transaction, often repeated. So I'm simply
going to RMA them.

The only difference with other OSes is that apparent bandwidth is somewhat
higher, though still low (USB 2.0 or less speeds). KB/t appears to be
frequently near 1024, where it is around 128 on FreeBSD (but then with higher
tps); the overhead of smaller transactions may explain the difference.

Will test KT_32G later to see how it fares.

Hans, thanks for `usbtest`.

A few question: In `usbtest`, does <Random> for the I/O size has any alignment
constraint on the size (like multiples of some power of 2, or only powers of
2)? And what about <Increasing>? In umass, is it possible to have longer
transaction then 128KB?

Thanks.

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