USB I/O draining my userspace (Ubuntu Natty 64b)

[is123 at zahav.net.il]

On Wed, 15 Jun 2011 16:19:08 +0300
Ira Abramov <Lists-Linux-IL at ira.abramov.org> wrote:

> First, an appology. I added another message on the RMS fiasco only to
> find out later the threads all died out and I was committing a faux pas.
> my appologies! please ignore I posted it if at all possible.

It's too late! You've done it now ;-)

> Second, here's my problem: I have here a workstation running an Athlon
> 3700+, and part of my job is to occasionally write out an image file to
> USB universal card reader, testing the product of my builds. The writing
> takes forever (since I haven't discovered how to get dd to write out the
> sparse image to the CF card sparsely). Also, untill I moved the card
> reader to one of the backpanel ports, the write would drag my entire
> environment to a halt at the same time - even the mouse pointer gets
> stuck at some point, until dd would finish. switching from front to back
> panel and adding the oflag=dsync option solved the freַ¯ing of the
> userspace but not the horrible writing speeds.

I do hourly rsyncs between two drives and it often causes my system to bog
heavily. I won't speculate on the reason because that topic is apparently
as inflammatory as the Stallman's boycott (!) but it does happen. It also
happens on my system with dd between disks. System in question is E8400 with
Seagate 16M Barracudas with Slackware and 2.6.29.6 kernel. I have seen this
behavior in every desktop OS I have tried (NetBSD, FreeBSD, OpenBSD,
Slackware, the "W" word) except for Slamd64 (no longer maintained).

> I have a feeling this is a major bug with the USBstorage driver or some
> related module, but as this is old hardware running on the latest kernel
> from Ubuntu, I am surprised. Anyone got a clue?
> 
> Thanks,
> Ira.
> 

Are you using the default blocksize for dd? It may not be optimal for your
USB device. I wonder if it would be possible to find out what blocksize the
device uses and if it would make a difference. I know bs does make a big
difference when copying big files to a physical disk.