Re: PM related performance degradation on OMAP3

[Kevin Hilman <khilman@ti.com>]

Gary Thomas <gary@mlbassoc.com> writes:

> On 2012-04-12 10:57, Kevin Hilman wrote:
>> +Felipe for EHCI question
>>
>> Gary Thomas<gary@mlbassoc.com>  writes:
>>
>> [...]
>>
>>> This worked a treat, thanks.  My network performance is better
>>> now, but still not what it was.  The same TFTP transfer now takes
>>> 71 seconds, so about 50% slower than on the 3.0 kernel.  Applying the
>>> second [unnamed] patch (arch/arm/mach-omap2/cpuidle34xx.c) made no difference.
>>
>> And does a CONFIG_PM=n kernel get you back to your v3.0 performance?
>
> Correct.
>

OK, I just tried your TFTP experiment on a 3530/Overo board with the
same smsc911x NIC that has GPIO interrupts, and I don't see much
difference between a PM-enabled v3.0 and a PM-enabled v3.3.

Are you TFTP'ing the file to an MMC filesystem?    Can you try to a
ramdisk[1]?  If you're using MMC, it could be MMC driver changes since
v3.0 that are actually causing your performance hit.

In my experiment, I TFTP'd a 24Mb file to a ramdisk, to make sure no
other drivers were invovled, and didn't see any major differences
between v3.0, v3.3, and v3.3 CONFIG_PM disabled.

Below are my results.  As you can see, all the results seem to be pretty
close to the same.  This test was not on a controlled, isolated network,
so the differences are probably explained by other network activity:

- v3.0 vanilla: PM enabled, CPUidle enabled
  - Received 25362406 bytes in 35.5 seconds
  - Received 25362406 bytes in 44.9 seconds
  - Received 25362406 bytes in 49.0 seconds
  - Received 25362406 bytes in 36.2 seconds
  - Received 25362406 bytes in 56.3 seconds
  - Received 25362406 bytes in 65.2 seconds
  - Received 25362406 bytes in 37.0 seconds

- v3.3: PM enabled, CPUidle enabled
 + GPIO fix (my for_3.4/fixes/gpio branch)
 + smsc911x regulator boot fix (Tony's omap/fix-smsc911x-regulator branch)
  - Received 25362406 bytes in 32.1 seconds
  - Received 25362406 bytes in 29.8 seconds
  - Received 25362406 bytes in 33.5 seconds
  - Received 25362406 bytes in 44.5 seconds
  - Received 25362406 bytes in 39.2 seconds
  - Received 25362406 bytes in 57.0 seconds
  - Received 25362406 bytes in 49.6 seconds

- v3.3: CONFIG_PM=n + branches above 
 + fix from Grazvydas for !CONFIG_PM case: [PATCH] ARM: OMAP: sram: fix BUG in dpll code for !PM case
 + disable CONFIG_OMAP_WATCHDOG which fails to boot when CONFIG_PM=y 
  - Received 25362406 bytes in 34.1 seconds
  - Received 25362406 bytes in 33.9 seconds
  - Received 25362406 bytes in 34.9 seconds
  - Received 25362406 bytes in 37.8 seconds
  - Received 25362406 bytes in 40.0 seconds
  - Received 25362406 bytes in 37.6 seconds
  - Received 25362406 bytes in 34.4 seconds


Kevin

[1] simple steps to make a ramdisk
mkfs.ext2 /dev/ram0
mkdir /tmp/rd
mount /dev/ram0 /tmp/rd
cd /tmp/rd
<then TFTP file here>