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Request for assistance with a bug

Apologies for this long message in advance :)

I'm an Ubuntu user who is having an ongoing problem with USB file transfers. This issue also seems to be affecting a significant number of other Ubuntu users, and I have also been reading reports of it appearing in other distros. I've reported it to the Ubuntu devs, however their investigations only went as far as testing for it on one or two computers, not finding it, and labeling it as low priority because it's a problem that "only some people get". Despite repeated attempts, I haven't been able to get them interested in investigating any further.

This is the issue: USB file transfers start off at full speed, the rapidly slow down, to speeds as low as 2mb/s, irrespective of the USB device, whether it's flash drive or a HDD. Many of the users that are being affected are experiencing it to different degrees, some get half the USB transfer speeds they are expecting, others get the full slowdown. Additionally, it doesn't always happen. In my experience, I've occasionally had a transfer speed at near the expected rate, but that's been rare. This problem also seems to affect Samba and UFS file transfers as well. I've got a DLink DNS-323 and I'm typically getting 2mb/s transfers over the network when copying files to it, which makes backing up my 100GB home folder, somewhat of a pain :)

Furthermore, this problem affects the GUI's responsiveness if a slow file transfer is allowed to continue running for a long time. What happens is that performance of the GUI slows to almost the point of being unusable, windows are being redrawn in slow motion and key presses take seconds to be detected. At the same time, the CPU is barely registering any activity. Cancelling the file transfer restores the system's performance immediately.

Most of the time this problem only shows up when copying a significant amount of data, somewhere over 100mb. Because it requires a lot of data to appear, I believe it's actually affecting a lot more users than are reporting it since it goes unnoticed while just copying a few text files around.

I own two computers, a laptop and a desktop and both are affected, and I'm not the only one in the Ubuntu forums who is reporting seeing this on multiple computers. It seems to be randomly affecting all types of hardware, Intel, AMD, ATI, nVidia, I've even seen one report of this on the eeePC.

This is the Ubuntu bug report: https://bugs.launchpad.net/ubuntu/+source/gvfs/+bug/197762

I recently happened upon a partial solution, that has at least enabled me to stop booting a live CD to copy files. I added "pci=routeirq" to my boot options and it restored about 80% of my USB file transfer speed on both my computers, though I'm still only getting 10mb/s via Samba to the DNS-323, at least it's sustained and it doesn't slow the GUI down, so I can live with it. This solution has also worked to various degrees for some of the other people that are affected, but there seems to be a new thread starting every other day now relating to this problem, so we (the affected users) need to find a permanent solution because although this isn't a "critical" problem, the frustration factor is huge.

Can anyone help me narrow down what is causing this problem, or at least point me towards someone who is capable of investigating it? At a guess, I'd say it's a kernel problem, but I really can't be sure. I need to find a developer who can reproduce the issue, but I don't know where to go, since it doesn't affect everyone, and it can be quite subtle. It would also be good to know if any Debian users have hit this problem. I've checked the Debian bug reports but I can't find any mention of it, but I could just be using the wrong keywords or package name.

Thanks in advance for any assistance or advice!

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