On Sun, 29 Apr 2007, [ISO-8859-15] Dirk Försterling wrote:
> Hello Linux-usb-users,
>
> I am experiencing a ridiculous network slowdown when connecting an external
> HDD.
> When I say "connecting", I mean it: Just loading ehci-hcd and attaching the
> disk.
> Read/write performance of the so attached disk isn't very fast, but would be
> sufficient for my purposes: about 4MB/s. I don't know what to expect from my
> old [EMAIL PROTECTED] anyway. However, as I want to use the disc over the
> network,
> the network slowdown really hurts. Transfer rates of the network-mounted drive
> drop to as low as 190K/s (nfs or SAMBA, doesn't matter).
>
> I'm using a VT6212 PCI add-on card with two USB ports in a VIA based
> mainboard.
> The kernel version is (now) 2.6.21.1 and was 2.4.34.4 before. With 2.4.34.4
> the slowdown was even worse.
>
> Below, there's some information included about the slow down and the system
> configuration.
>
> Any idea about how to fix that slowdown?
David Brownell has suggested that it might be a hardware problem in the
PCI card's controller hardware, that it doesn't stop doing DMA when it is
told to. Of course that's just a guess; there's no way to tell at this
point. (In fact there may be no way to tell at all, leaving little choice
but to buy a different brand of PCI USB card and see if it works any
better...)
You might be able to get some more useful information by doing this: Turn
on CONFIG_USB_DEBUG and rebuild the USB drivers. Then with the new
drivers loaded, plug in the USB drive and unplug it again a little while
later. Presumably the overall system slowdown will continue. Post the
output from dmesg so we can see if anything strange shows up in the log.
And include also the contents of the files in
/sys/class/usb_host/usb_host1
They contain debugging information about the EHCI controller and driver.
Alan Stern
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