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Old 05-06-2010, 02:16 AM
AceLan Kao
 
Default fsl-imx51: Enabling function tracer and function profiler of the ftrace

Dear Chase,

Sorry, I sent to the wrong mailing list, thanks for the reminding.

The fsl-imx51 branch doesn't support too much features of the ftrace,
including FUNCTION_GRAPH_TRACER, DYNAMIC_FTRACE, MMIOTRACE
Do you think is there any other useful options should be enabled?
I can try to see if they're supported in the fsl-imx51 branch.

Best regards,
AceLan Kao.

2010/5/5 Chase Douglas <chase.douglas@canonical.com>:
> On Wed, May 5, 2010 at 2:39 AM, AceLan Kao <acelan.kao@canonical.com> wrote:
>> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux-fsl-imx51/+bug/575537
>>
>> Function tracer is the most important tracer of the ftrace, it has the
>> ability to trace practically every function in the kernel. We need to
>> enable this option for the further debugging.
>> And according to bug 570389, function profiler is very useful for the
>> performance analysis, so please consider enable this option as well.
>>
>> The following changes since commit 0e971008ddb4fc58c6122b8cdca303f3b3d87bc0:
>> *AceLan Kao (1):
>> * * * *[Lucid][SRU] fsl-imx51: Enabling function tracer and function
>> profiler of the ftrace
>>
>> are available in the git repository at:
>>
>> *git://kernel.ubuntu.com/acelan/ubuntu-lucid lp575537
>
> Does this produce an identical config to the x86 tree now? There are
> quite a few ftrace options, so we might as well ensure they are all
> synced up now rather than later.
>
> Also, this isn't NDA, so it should be posted to ubuntu-kernel mailing
> list, right?
>
> Assuming the config matches the x86 config:
> Acked-by: Chase Douglas <chase.douglas@canonical.com>
>
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--
Chia-Lin Kao(AceLan)
http://blog.acelan.idv.tw/
E-Mail: acelan.kaoATcanonical.com (s/AT/@/)

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Old 05-06-2010, 09:56 AM
Chase Douglas
 
Default fsl-imx51: Enabling function tracer and function profiler of the ftrace

On Wed, May 5, 2010 at 10:18 PM, AceLan Kao <acelan.kao@canonical.com> wrote:
> The fsl-imx51 branch doesn't support too much features of the ftrace,
> including FUNCTION_GRAPH_TRACER, DYNAMIC_FTRACE, MMIOTRACE
> Do you think is there any other useful options should be enabled?
> I can try to see if they're supported in the fsl-imx51 branch.

if DYNAMIC_FTRACE is not supported, then we don't want any of this
enabled by default. DYNAMIC_FTRACE is the magic that lets you turn
tracing on and off at runtime. If you can't do that, then everything
will be traced all the time. This would hurt performance.

It looks like this could be resolved soon for ARM though:
http://thread.gmane.org/gmane.linux.kernel/949812, but I haven't read
all the replies, and it hasn't landed in Linus' tree nor in Steve
Rostedt's.

Thus, NACK from me for enabling ftrace on any ARM platform until it
has DYNAMIC_FTRACE support. Of course, we can still make debug kernels
for specific testing, we just can't enable it for a release kernel.

-- Chase

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