I have added nohlt and seems no any changes wrt. usb storage performance. But the following test is interesting, just run a 'busy' in background and increas usb storage performance triple or 4 times, and killing the 'busy' task will make usb storage performance poor like before.
see my test below: root@tom-panda:~# ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) root@tom-panda:~# dd if=/dev/sda iflag=direct of=/dev/null bs=128K count=32 32+0 records in 32+0 records out 4194304 bytes (4.2 MB) copied, 5.9715 s, 702 kB/s root@tom-panda:~# cat /proc/cmdline ro elevator=noop vram=32M mem=456M@0x80000000 mem=512M@0xA0000000 root=UUID=a957f519-7a09-48d9- a60d-b15883901edf fixrtc quiet splash console=ttyO2,115200n8 serialtty=ttyO2 earlyprintk root@tom-panda:~# ./busy& [1] 1183 root@tom-panda:~# cat busy #/bin/sh x=1 while [ true ] do x=$(( $x + 1 )) done root@tom-panda:~# dd if=/dev/sda iflag=direct of=/dev/null bs=128K count=32 32+0 records in 32+0 records out 4194304 bytes (4.2 MB) copied, 0.771301 s, 5.4 MB/s root@tom-panda:~# kill -9 1183 root@tom-panda:~# sleep 3 [1]+ Killed ./busy root@tom-panda:~# dd if=/dev/sda iflag=direct of=/dev/null bs=128K count=32 32+0 records in 32+0 records out 4194304 bytes (4.2 MB) copied, 3.40616 s, 1.2 MB/s -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/709245 Title: panda: USB disk IO slow To manage notifications about this bug go to: https://bugs.launchpad.net/linaro-ubuntu/+bug/709245/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs