Comment 0 for bug 709245

My Panda's USB seems to be significantly slower than a Beagle C4.

hdparm shows buffered reads as ~12MB/s on the Panda, and about ~20-25MB/s on a Beagle C4 from the same
external Lacie USB disk.

Kernel is 2.6.37-1002-linaro-omap

Disk shows as:

[ 5.170440] scsi 0:0:0:0: Direct-Access LaCie d2 quadra PQ: 0 ANSI: 4
[ 5.172546] sd 0:0:0:0: Attached scsi generic sg0 type 0
[ 5.175415] sd 0:0:0:0: [sda] 976773168 512-byte logical blocks: (500 GB/465 GiB)

The board is otherwise idle during the test.

Doing perf_2.6.37-12 record -a dd if=/dev/sda of=/dev/null bs=4096 count=100000

shows :
    81.41% swapper [kernel.kallsyms] [k] default_idle
     6.33% dd [kernel.kallsyms] [k] __copy_to_user
     0.94% swapper [kernel.kallsyms] [k] cpu_idle
     0.51% dd [kernel.kallsyms] [k] __make_request
     0.51% perf_2.6.37-12 [kernel.kallsyms] [k] __copy_from_user

which suggests it's not CPU constrained.

Dave