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[Bug 709245] Re: panda: USB disk IO slow

To: linaro-release@xxxxxxxxxxxxxxxxxxx
From: Jani Monoses <jani@xxxxxxxxxx>
Date: Mon, 01 Aug 2011 10:49:28 -0000
Reply-to: Bug 709245 <709245@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

I see the same behaviour without ethernet plugged in, and pinging the
panda via wlan0. Is that chip too on the same USB controller?

5x speed increase on write when pinging with -i.0001

jani@panda:~$ time dd if=/dev/zero of=alma bs=4M count=1024
1024+0 records in
1024+0 records out
4294967296 bytes (4.3 GB) copied, 1451.47 s, 3.0 MB/s

real	25m7.935s
user	0m0.023s
sys	1m24.266s


jani@panda:~$ time dd if=/dev/zero of=alma2 bs=4M count=1024
1024+0 records in
1024+0 records out
4294967296 bytes (4.3 GB) copied, 267.908 s, 16.0 MB/s

real	4m30.361s
user	0m0.016s
sys	1m15.844s

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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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