On 1/14/2011 10:06 AM, Josef Wolf wrote:
Hello folks.
I am trying to track a performance bottleneck on the USB interface. The strange thing is that I sometimes get good performance and other times bad performance.
For example, I have a memory stick which should go about 5MB/s for write.
From this stick, I sometimes get the promised 5MB/s. But sometimes I get only about 120kb/s. It is the same stick, plugged into the same port, without reboots. But for some strange reason, sometimes it is recognized as a "full speed device" (this is the slow mode) and sometimes as a "high speed device" (this is the fast mode). Please check the two excerpts from /var/log/messages below.
This is opensuse-11.2 running on a 2GHz Athlon dual core 4850e with USB2.0 on-board.
Any ideas?
Jan 13 17:15:42 raven kernel: [4988831.356060] usb 6-3: new full speed USB device using ohci_hcd and address 10 Jan 13 17:15:42 raven kernel: [4988831.496420] usb 6-3: not running at top speed; connect to a high speed hub
Jan 14 18:47:12 raven kernel: [5080721.042097] usb 2-6: new high speed USB device using ehci_hcd and address 8 Jan 14 18:47:12 raven kernel: [5080721.158891] usb 2-6: New USB device found, idVendor=1307, idProduct=0165
You say they are being plugged into the EXACT SAME PORT but your examples from two consecutive days suggests they were actually in different ports. Its not unusual for machines to have ports in the same machine that use different controllers even when they sit close to each other. However, if you are very sure it is on the same port, is it possible that something else plugged in to another port on the same header would pull both ports down to USB 1.1 speed. Early USB 2.0 implementations did not not have good transaction translators on each port. Any slow speed device on the same controller could bring the whole bus down to 12mg. See this article http://www.analogzone.com/iot_0203.pdf -- _____________________________________ ---This space for rent--- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org