Howto make perf probe work

Howto make perf probe work

[OSDepend]

Hi all,
	Is there any way to use perf probe to add new tracepoint like pagefault enter/exit?
	
	When I type perf probe fault:10
	I always get the error as follow:

		Debuginfo-analysis is not supported.
		Error: Failed to add events. (-38)
	
	What exactly i miss to get the perf probe work correctly?

Best,
Chen

2013-04-01



zhengchen

Re: Howto make perf probe work

[OSDepend]

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>HI,
>Please enable kprobe_event config option in the kernel and build the same
>and boot the board using it. Then please try to add event using perf probe
>command

Thanks very much for your reply, and I already enable DEBUG_KPROBE_EVENT in kernel.
I did success in "perf probe handle_mm_fault".

But when i want to to "perf probe" other Kernel symbol, such as do_page_fault.
I came across other problems:
Added new event:
Failed to write event: Invalid argument
Error: Failed to add events. (-1)
And when i type perf probe page_fault_entry:
Kernel symbol 'page_fault_entry' not found.
Error: Failed to add events. (-2)
Please notice that "do_page_fault" and "page_fault_entry" are all Kernel symbols, which canbe find in  "/proc/kallsyms", but not recorgonized by perf (or even kprobe).
Any idea for that?

Best,
Chen

>>On Sun, Mar 31, 2013 at 11:00 PM, OSDepend <osdepend-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>Hi all,
>>        Is there any way to use perf probe to add new tracepoint like pagefault enter/exit?
>>        When I type perf probe fault:10
>>       I always get the error as follow:
>>                Debuginfo-analysis is not supported.
>>                Error: Failed to add events. (-38)
>>        What exactly i miss to get the perf probe work correctly?
>>Best,
>>Chen

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Fw: Re: Re: Howto make perf probe work

[OSDepend]

>HI,
>Please enable kprobe_event config option in the kernel and build the same
>and boot the board using it. Then please try to add event using perf probe
>command

Thanks very much for your reply, and I already enable DEBUG_KPROBE_EVENT in kernel.
I did success in "perf probe handle_mm_fault".

But when i want to to "perf probe" other Kernel symbol, such as do_page_fault.
I came across other problems:
    Added new event:
    Failed to write event: Invalid argument
    Error: Failed to add events. (-1)
And when i type perf probe page_fault_entry:
    Kernel symbol 'page_fault_entry' not found.
    Error: Failed to add events. (-2)
Please notice that "do_page_fault" and "page_fault_entry" are all Kernel symbols, which canbe find in  "/proc/kallsyms", but not recorgonized by perf (or even kprobe).
Any idea for that?

Best,
Chen

>>On Sun, Mar 31, 2013 at 11:00 PM, OSDepend <osdepend@gmail.com> wrote:
>>Hi all,
>>        Is there any way to use perf probe to add new tracepoint like pagefault enter/exit?
>>        When I type perf probe fault:10
>>       I always get the error as follow:
>>                Debuginfo-analysis is not supported.
>>                Error: Failed to add events. (-38)
>>        What exactly i miss to get the perf probe work correctly?
>>Best,
>>Chen

Re: Fw: Re: Re: Howto make perf probe work

[Namhyung Kim]

> >HI,
> >Please enable kprobe_event config option in the kernel and build the same
> >and boot the board using it. Then please try to add event using perf probe
> >command
> 
> Thanks very much for your reply, and I already enable DEBUG_KPROBE_EVENT in kernel.
> I did success in "perf probe handle_mm_fault".
> 
> But when i want to to "perf probe" other Kernel symbol, such as do_page_fault.
> I came across other problems:
>     Added new event:
>     Failed to write event: Invalid argument
>     Error: Failed to add events. (-1)
> And when i type perf probe page_fault_entry:
>     Kernel symbol 'page_fault_entry' not found.
>     Error: Failed to add events. (-2)
> Please notice that "do_page_fault" and "page_fault_entry" are all Kernel symbols, which canbe find in  "/proc/kallsyms", but not recorgonized by perf (or even kprobe).
> Any idea for that?

For some reason, do_page_fault() is marked as __kprobe on some arch
which means it cannot be probed.

Thanks,
Namhyung

Re: Re: Fw: Re: Re: Howto make perf probe work

[OSDepend]

Hi Kim,

> > >HI,
> > >Please enable kprobe_event config option in the kernel and build the same
> > >and boot the board using it. Then please try to add event using perf probe
> > >command
> > 
> > Thanks very much for your reply, and I already enable DEBUG_KPROBE_EVENT in kernel.
> > I did success in "perf probe handle_mm_fault".
> > 
> > But when i want to to "perf probe" other Kernel symbol, such as do_page_fault.
> > I came across other problems:
> >     Added new event:
> >     Failed to write event: Invalid argument
> >     Error: Failed to add events. (-1)
> > And when i type perf probe page_fault_entry:
> >     Kernel symbol 'page_fault_entry' not found.
> >     Error: Failed to add events. (-2)
> > Please notice that "do_page_fault" and "page_fault_entry" are all Kernel symbols, which canbe find in  "/proc/kallsyms", but not recorgonized by perf (or even kprobe).
> > Any idea for that?
> For some reason, do_page_fault() is marked as __kprobe on some arch
> which means it cannot be probed.
> Thanks,
> Namhyung

My kernel is runing on X86_64 arch, is there any chance for me to get the do_page_fault() entry/exit work?
Or How can i add a exit tracepoint for handle_mm_fault()? so I can calculate the latency of that fault handle function?

Best,
Chen

Re: Fw: Re: Re: Howto make perf probe work

[Namhyung Kim]

Hi,

On Tue, 2 Apr 2013 17:11:01 +0800,
>> For some reason, do_page_fault() is marked as __kprobe on some arch
>> which means it cannot be probed.
>
> My kernel is runing on X86_64 arch, is there any chance for me to get the do_page_fault() entry/exit work?

nope, AFAIK.


> Or How can i add a exit tracepoint for handle_mm_fault()? so I can calculate the latency of that fault handle function?

Try "perf probe -a entry=handle_mm_fault -a exit=handle_mm_fault%return"


Thanks,
Namhyung

Re: Re: Fw: Re: Re: Howto make perf probe work

[OSDepend]

Hi,

> > Or How can i add a exit tracepoint for handle_mm_fault()? so I can calculate the latency of that fault handle function?

> Try "perf probe -a entry=handle_mm_fault -a exit=handle_mm_fault%return"

That's works nicely for me! 
Thanks a lot!!

> On Tue, 2 Apr 2013 17:11:01 +0800,
> >> For some reason, do_page_fault() is marked as __kprobe on some arch
> >> which means it cannot be probed.
> >
> > My kernel is runing on X86_64 arch, is there any chance for me to get the do_page_fault() entry/exit work?
> nope, AFAIK.
Is there any guide for us to decide which tracepoint (or other kernel symbol) canbe used, and which cannot? 
For some of the kallsyms cannot be used directly. Such as  do_raw_spin_lock.
	perf probe -a test=do_raw_spin_lock
    Fatal: Kernel symbol 'do_raw_spin_lock' not found - probe not added. 
		
Best,
Chen

Re: Fw: Re: Re: Howto make perf probe work

[Namhyung Kim]

Hi,

On Thu, 4 Apr 2013 01:28:34 +0800, OSDepend wrote:
>> On Tue, 2 Apr 2013 17:11:01 +0800, OSDepend wrote:
>> >> For some reason, do_page_fault() is marked as __kprobe on some arch
>> >> which means it cannot be probed.
>> >
>> > My kernel is runing on X86_64 arch, is there any chance for me to get the do_page_fault() entry/exit work?
>> nope, AFAIK.
> Is there any guide for us to decide which tracepoint (or other kernel symbol) canbe used, and which cannot? 
> For some of the kallsyms cannot be used directly. Such as  do_raw_spin_lock.
> 	perf probe -a test=do_raw_spin_lock
>     Fatal: Kernel symbol 'do_raw_spin_lock' not found - probe not added. 

Hmm.. it seems not, currently.

Maybe we can change perf to output the symbol was not able to be probed
after checking symbol address and it's between
__kprobes_text_{start,end}.

I'll take a look at it later.

Thanks,
Namhyung