On Sun, 13 Jan 2013, Piergiorgio Sartor wrote: > Hi Alan, > > Happy New Year! I hope you had a good holiday break. > I removed the previous short patch to ehci-q.c and applied > this second one. > > After some extensive testing, I could not reproduce the > issue and dmesg showed the ususl "async off" and "async on" > messages, the second as soon as I started to read the HDDs. > > Performance wise, it seems to me better than ever, I mean > I saw regular transfer of above 4000 KB/sec per disk. > > Even with 2 processes reading the 10 HDDs, the data rate > was about 3800 KB/sec. > > Next step? Okay, I figured out what the problem is. It really is a bug in ehci-hcd; the driver doesn't do what the spec requires when unlinking more than one QH at a time. Although the driver could be fixed, it will be easier to stick with the old approach and never unlink more than one QH. Doing two or more at once is pretty rare, so it doesn't much matter if they take a little longer. I'll send a patch that does this properly in the near future, for you to test. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
