Le 13/05/2016 23:53, Rick Stevens a écrit :
On 05/13/2016 02:33 PM, François Patte wrote:
> Le 13/05/2016 18:45, Rick Stevens a écrit :
>> On 05/13/2016 02:12 AM, François Patte wrote:
>>> Bonjour,
>>>
>>> The issue now is about wifi connections and usb (!!)
>>>
>>> If I plug an external usb harddrive, the wifi connection becomes
>>> awfull:
>>> I tested the rate of transfert from one computer to my updated laptop,
>>> using this:
>>>
>>> dd if=/dev/zero of=test bs=100M count=1; scp test me@laptop:/dev/null;
>>>
>>> Without any usb hdd plugged, the rate begins at 4.7MB/s and falls down
>>> to 2.4MB/s which is acceptable I think.
>>>
>>> With an usb hdd plugged (I tested with several devices), the rate
>>> quickly falls down to 100KB/s sometimes to 20KB/s and sometimes remains
>>> completely stalled. Moreover, the wifi connection is very often
>>> disconnected (even when there is no tranfert of data at all).
>>
>> It is not uncommon for a laptop's wifi to be on the USB bus. My Dell
>> laptop does precisely this (it is on one of the EHCI controllers).
>
> Yes, it is a laptop Dell (latitude e6540)
Ok, it could (and I mean "_could_") be a firmware issue with the
underlying USB hardware. I can only suggest two things at this point.
Item 1: See if you can plug the HDD into a port that's on a
different
USB device on the machine. You can use the "lsusb -t" utility (as root)
to show you a tree of what's on the USB ports. Mine looks like:
[root@golem4 ~]# lsusb -t
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/8p, 480M
|__ Port 5: Dev 3, If 0, Class=Wireless, Driver=btusb, 12M
|__ Port 5: Dev 3, If 1, Class=Wireless, Driver=btusb, 12M
|__ Port 6: Dev 4, If 0, Class=Vendor Specific Class, Driver=, 480M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/6p, 480M
|__ Port 4: Dev 4, If 0, Class=Video, Driver=uvcvideo, 480M
|__ Port 4: Dev 4, If 1, Class=Video, Driver=uvcvideo, 480M
The first ehci device has both the bluetooth and wifi on it. The second
ehci device has the webcam on it. Try to plug the HDD into a port
that's not shared with the "wireless" stuff (verify with the lsusb
command). If you can find one, see if that helps.
I get exactly the same answer as yours for lsusb -t and the problem
remains regardless the usb port where I plug the hdd.
But now the problem become worse: with or without a hdd plugged, the
wifi connection is unusable because the bitrate falls down in a few
seconds (from 4MB/s to 20KB/s and, after that, remains stalled for a
long time)...
Could it be a hardware problem and, if yes, is there a way to test the
integrity of the wifi card?
Thank you
--
François Patte
UFR de mathématiques et informatique
Laboratoire CNRS MAP5, UMR 8145
Université Paris Descartes
45, rue des Saints Pères
F-75270 Paris Cedex 06
Tél. +33 (0)1 8394 5849
http://www.math-info.univ-paris5.fr/~patte