Alan Stern wrote:
On Tue, 16 May 2006, aermongk wrote:
Hi Alan,
Thanks for your response. Comments below.
...
But when I used 2 PC's with 2 channels per PC. again in
Adhoc mode and ran ttcp on both channels simultaneously,
the speed of each channel went down by 1/3 to 1/2 of the
expected speed. I suspect that it is USB related.
Do you have any evidence to back up this suspicion? For example, what
happens if you run with 1 channel per PC but with a second USB device
(like a flash disk) installed and in use?
I did experiment as you've suggested by adding USB flash disk with 1
channel.
The USB flash disk doesn't degrade the performance of the wireless. I
did try
read/write the USB flash drive and transmit onto wireless at the same time,
the speed of wireless device is still at its expected value
(20-25Mbps). Then
I remove USB flash drive and add another channel and try again. Same
result,
speed of each channel is down'ed by half. That means that the wireless
driver
is not sending out fast enough, humm!!!
And it indicates that this may not be a USB throughput problem.
I check the "wMaxPacketSize", it is already set to 64 when the
probe function is called. Is there anything that I could do to
enhance the performance.
Which wMaxPacketSize did you check? Is it the value for endpoint 0 or the
value for one of the bulk endpoints?
I browse at the driver code, endpoint 0 is for control (setting
registers in the device)
and endpoint 1 is for data transmission/reception. I looked at both
endpoints and both
are set to 64.
This doesn't seem consistent with what you wrote above. If you're getting
20-25 Mb/s throughput then you must be using high-speed USB -- full speed
runs only at 12 Mb/s. (Or does the wireless protocol use data
compression?) But full-speed bulk endpoints are required to have a
maxpacket size of 512, not 64. Possibly endpoint 1 is interrupt, not
bulk.
My apology for using the term "full speed", my "full speed" is meant to
be wireless
thoughput and not USB full speed. I am using high-speed USB for my test.
What does /proc/bus/usb/devices say about the wireless device?
Here is usbtree report:
[EMAIL PROTECTED] rt2570]# usbtree
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/8p, 480M
|__ Port 1: Dev 2, If 0, Class=vend., Driver=none, 480M
|__ Port 2: Dev 3, If 0, Class=vend., Driver=none, 480M
|__ Port 4: Dev 4, If 0, Class=stor., Driver=usb-storage, 480M
Here is my /proc/bus/usb/devices. The wirelesss device name is rtusb.
[EMAIL PROTECTED] rt2570]# cat /proc/bus/usb/devices
T: Bus=05 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 1.10 Cls=09(hub ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.16.15 uhci_hcd
S: Product=UHCI Host Controller
S: SerialNumber=0000:00:1d.3
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=255ms
T: Bus=04 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 1.10 Cls=09(hub ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.16.15 uhci_hcd
S: Product=UHCI Host Controller
S: SerialNumber=0000:00:1d.2
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=255ms
T: Bus=03 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 1.10 Cls=09(hub ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.16.15 uhci_hcd
S: Product=UHCI Host Controller
S: SerialNumber=0000:00:1d.1
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=255ms
T: Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 1.10 Cls=09(hub ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.16.15 uhci_hcd
S: Product=UHCI Host Controller
S: SerialNumber=0000:00:1d.0
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=255ms
T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 8
B: Alloc= 0/800 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=01 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.16.15 ehci_hcd
S: Product=EHCI Host Controller
S: SerialNumber=0000:00:1d.7
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=256ms
T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=2001 ProdID=3c00 Rev= 0.01
S: Manufacturer=ANI
S: Product=802.11g WLAN Adapter
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=300mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=rtusb
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 3 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=2001 ProdID=3c00 Rev= 0.01
S: Manufacturer=ANI
S: Product=802.11g WLAN Adapter
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=300mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=rtusb
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
T: Bus=01 Lev=01 Prnt=01 Port=03 Cnt=03 Dev#= 4 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=07cc ProdID=0501 Rev=91.44
S: Manufacturer=USB2.0
S: Product=CardReader
S: SerialNumber=1234609
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=500mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I will continue to look at the driver code to see if I can spot
anything. I am currently
using rt2570 driver from Ralink (http://rt2x00.serialmonkey.com) and
device I use is
D-Link DWL-G122. I will also educate myself more about USB.
Perhaps you can get some useful information from usbmon. The instructions
for using it are in the kernel source, Documentation/usb/usbmon.txt.
Alan Stern
I 'll try that.
Adisorn.
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