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[Tobin Davis <709245@xxxxxxxxxxxxxxxxxx>]

Tested the Maverick kernel in proposed.  While I am not seeing much
improvement, the kernel at least doesn't break other things.

The following is the results of testing on a PATA drive in an external enclosure:
-- BEFORE --
Linux panda5 2.6.35-903-omap4 #24-Ubuntu SMP PREEMPT Thu Sep 1 20:37:40 UTC 2011 armv7l GNU/Linux
/dev/sda:
 Timing cached reads:   388 MB in  2.00 seconds = 193.66 MB/sec
 Timing buffered disk reads:   54 MB in  3.10 seconds =  17.45 MB/sec
-- AFTER --
Linux panda5 2.6.35-903-omap4 #25-Ubuntu SMP PREEMPT Tue Sep 20 21:02:11 UTC 2011 armv7l GNU/Linux
/dev/sda:
 Timing cached reads:   402 MB in  2.00 seconds = 200.71 MB/sec
 Timing buffered disk reads:   70 MB in  3.07 seconds =  22.83 MB/sec


** Tags removed: verification-needed-maverick
** Tags added: verification-done-maverick

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https://bugs.launchpad.net/bugs/709245

Title:
  ARM SMP scheduler performance bug

Status in Linaro Ubuntu Evaluation Builds:
  Fix Committed
Status in Linaro Linux:
  Confirmed
Status in OEM Priority Project:
  Fix Committed
Status in OEM Priority Project maverick series:
  Fix Committed
Status in OEM Priority Project natty series:
  Fix Committed
Status in OEM Priority Project oneiric series:
  Fix Released
Status in “linux-ti-omap4” package in Ubuntu:
  Fix Released
Status in “linux-ti-omap4” source package in Maverick:
  Fix Committed
Status in “linux-ti-omap4” source package in Natty:
  Fix Committed
Status in “linux-ti-omap4” source package in Oneiric:
  Fix Released

Bug description:
  Original Bug name: "panda: USB disk IO slow"

  This bug effects ARM Cortex A9 cores, snowball, nvidia, OMAP 4, and
  other Cortex A9 processors.  Problem is in Fedora ARM builds also so
  not limited to Ubuntu.

  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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