On 06/01/2011 09:56 AM, Somebody in the thread at some point said: Hi - >>> Note: I get crappy performance with the network *up*, as long as >>> there's no traffic. >> I had a go a reproducing this also on a 2.6.38-based kernel on Panda. >> I was thinking it sounds a bit like USB suspend (not the same as >> to see if there was something obvious to hack suspend disabled but >> didn't see anything useful. > > try disabling pm_runtime completely. Thanks for the idea --> # CONFIG_PM_RUNTIME is not set Acts the same root@linaro:~# dd if=/dev/zero of=/media/FAD8-72F0/dump bs=4096 count=10240 10240+0 records in 10240+0 records out 41943040 bytes (42 MB) copied, 16.045 s, 2.6 MB/s root@linaro:~# dd if=/dev/zero of=/media/FAD8-72F0/dump bs=4096 count=10240 10240+0 records in 10240+0 records out 41943040 bytes (42 MB) copied, 17.28 s, 2.4 MB/s root@linaro:~# dd if=/dev/zero of=/media/FAD8-72F0/dump bs=4096 count=10240 10240+0 records in 10240+0 records out 41943040 bytes (42 MB) copied, 11.8782 s, 3.5 MB/s root@linaro:~# dd if=/dev/zero of=/media/FAD8-72F0/dump bs=4096 count=10240 10240+0 records in 10240+0 records out 41943040 bytes (42 MB) copied, 12.368 s, 3.4 MB/s CONFIG_OMAP_WATCHDOG blows an imprecise external about with RUNTIME_PM disabled BTW, I guess that peripheral unit isn't clocked without it.

> Or does it happen with reads too? With both the sata drive (sda) and flash drive (sdb) (both usb) connected, and network (also usb) up and running, I did some raw read tests: dd if=/dev/sda1 of=/dev/null bs=4096 count=102400 dd if=/dev/sdb1 of=/dev/null bs=4096 count=102400 sda              9.4  MB/sec sda+ping        23.4 sdb              7.8 sdb+ping        21.3 both            14.7 each (29.4 total) both+ping       14.0 each (28.0 total) So, the problem seems to happen if you have one usb-storage active and no other usb activity, but other activity (either another usb-storage or ethernet pings) seems to work around the problem.

a serial port connected to a 9600 baud character generator, and got good performance. Likewise with a usb mouse, as long as I wiggled the mouse during the test.