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Message #00405
Re: [Bug 709245] Re: panda: USB disk IO slow
On Mon, 1 Aug 2011, Michael Sparmann wrote:
> No noticable improvement: http://paste.ubuntu.com/656498/
The nohlt argument prevents the idle power saving code from being called
at all. So if that doesn't help the USB case either than it is unlikely
that anything related to sleep modes.
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https://bugs.launchpad.net/bugs/709245
Title:
panda: USB disk IO slow
Status in Linaro Ubuntu Evaluation Builds:
Confirmed
Status in Linaro Linux:
Confirmed
Status in “linux-ti-omap4” package in Ubuntu:
Confirmed
Status in “linux-ti-omap4” source package in Oneiric:
Confirmed
Bug description:
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
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