Re: [PATCH v1 3/3] perf probe: Generate hash event for long symbol

[Leo Yan]

On 10/11/2024 4:07 AM, Masami Hiramatsu (Google) wrote:

[...]

>>> OK, personally, I recommend you to specify event name instead of generating
>>> long event name in this case. But I understand sometimes this kind of feature
>>> is good for someone.
>>
>> Sometimes, users try to add probe for long symbol and returns error, but there
>>   have no clue for proceeding.
> 
> OK, no warning messsage is not good.
> It should warn them to recommend adding it with their own event name too.

Okay, will do this in next spin.

>> Either we automatically generate a hashed name, or a guidance in the failure
>> log for setting event name would be helpful. If you have concern for hashed
>> name, maybe we can refine the log to give info for setting event name?
> 
> Yeah, I think this long event name is not useful for user to type.

Agreed.

>>> BTW, I would like to confirm. Can't we demangle the symbol name and parse it?
>>
>> I did test for C++ demangle symbols with the command:
>>
>>    perf probe -x /mnt/test_cpp_mangle -F --demangle
>>
>> The command doesn't work as I cannot see it output correctly for demangled
>> symbols. But I don't look into details why this does not work at my side.
> 
> Oops, that is another issue to be solved.

After install libiberty, then I can see the tool can show demangled symbols.
However, I found another issue for probing demangle symbol, please see details
in below patch and let me know if makes sense.

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