linux-kernel - Re: dynamic ftrace

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Message-ID: <4B21F4F6.5080600@monstr.eu>
Date:	Fri, 11 Dec 2009 08:29:58 +0100
From:	Michal Simek <monstr@...str.eu>
To:	rostedt@...dmis.org
CC:	wuzhangjin@...il.com, linux-kernel@...r.kernel.org,
	John Williams <john.williams@...alogix.com>
Subject: Re: dynamic ftrace - graph

Steven Rostedt wrote:
> Hi Michal,
> 
> Sorry for such a late reply, you sent this email to me at the worst
> time. My wife was having shoulder surgery and I heading for a
> conference. I fell very far behind in email and I only now just noticed
> this.

No problem. I prepared Microblaze ftrace patches. You can find them in 
linux-next. I am going to send pull request to Linus soon that's why if 
you have any your comments please let me know.

> 
> 
> I'll answer these ever though you may already figured it out.
> 
> On Mon, 2009-11-09 at 17:52 +0100, Michal Simek wrote:
>> Hi Steve and others,
>>
>> I have working dynamic ftrace function. :-)
>>
>> I look at __ftrace_modify_code function and I have one question about.
>> Below are function which are called when I enable function_graph.
>>
>> I personally think that make more sense to call 
>> ftrace_enable_ftrace_graph_caller before ftrace_update_ftrace_func.
>> The reason for it is that graph_caller enable calling graph tracing 
>> which should be setup before ftrace_update_ftrace_func which enable 
>> whole tracing function.
> 
> Have you seen any difference in output with this?

I haven't tested it. It was just suggestion. I don't know if is relevant 
or not.

Michal

> 
> I never thought about this order too much.
> 
> -- Steve
> 
>>
>>
>> # cd ; mkdir /debug; mount -t debugfs none /debug; cat 
>> /debug/tracing/available_tracers; echo function_graph > 
>> /debug/tracing/current_tracer;echo 0 > /debug/tra
>> cing/tracing_enabled;cat /debug/tracing/trace | head -n 10
>> function_graph function sched_switch nop
>>
>> ftrace_update_ftrace_func 0xc0009100 0xc00091c4, 0xb000c000, 0x32809100
>> ftrace_enable_ftrace_graph_caller
>> # tracer: function_graph
>>
>>
>> For disabling graph trace is sequence ok I think.
>>
>> # echo function > /debug/tracing/current_tracer
>> ftrace_disable_ftrace_graph_caller
>> ftrace_update_ftrace_func 0xc006afe4 0xc00091c4, 0xb000c006, 0x3280afe4
>>
>>
>> What do you think?
>>
>> Thanks,
>> Michal
>>
>>
> 
> 


-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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