On Fri, 3 Aug 2012, mat brown wrote:

> Already done as requested by the Ubuntu devs.  File is here:
> https://launchpadlibrarian.net/111697628/usbmon.out
> 
> The transfer which created that file was generated using dd
> if=/dev/zero of=/media/littlun/tmp oflag=direct bs=120K count=2K

It's odd.  The usbmon log shows things working pretty well most of the
time, with transfer speeds around 200 Mb/s, but every now and then a
single 120-KB transfer takes more than half a second!

I have no idea why.  We can rule out hardware problems because it 
doesn't happen under Fedora.  Maybe interrupt delivery gets delayed 
somehow under Ubuntu, or maybe something is different in the xhci-hcd 
driver.  Can you compare the driver source files?

To do more serious testing will require you to build your own kernel, 
or at least, your own version of the driver.

Alan Stern

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https://bugs.launchpad.net/bugs/1032342

Title:
  090c:1000 file transfer to/from USB 2.0 flash drive, via 3.0 port at
  best 50-60 Mb/s

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