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SubjectRe: [RFC PATCH 2/5] tracing/events: nicer print format for parsing
Steven Rostedt wrote:
> On Tue, 9 Jun 2009, Frederic Weisbecker wrote:
>>
>>> The language that is added by this patch is of the following:
>>>
>>> * FMT := constant string FMT | COMMAND FMT | empty
>>> * COMMAND := <TYPE:FIELD> | <mask:FIELD:DELIM:MASKS> | <sym:FIELD:SYMBOLS> |
>>> * <if:FIELD:TRUE:FALSE>
>>> * TYPE := int | hex | ptr | string | strarray
>>> * FIELD := defined by the event structure
>>> * MASKS := MASK=NAME,MASKS | MASK=NAME
>>> * MASK := the bit mask to match
>>> * DELIM := delimiter to separate the fields. None and ':' are both allowed
>>> * SYMBOLS := SYM=NAME,SYMBOLS | SYM=NAME
>>> * SYM := the symbol value to test against
>>> * TRUE := print when field is non zero
>>> * FALSE := print when field is zero or NULL
>>> * NAME := the name to write when a match is found
>>> *
>>> * A '\<' would print '<'
>>
>> But I wonder if the above new language is not breaking the charm
>> of the TRACE_EVENT(), which charm is that it's easy to implement (hopefully).
>>
>> Everyone knows the printk formats. And I guess this new thing is easy and
>> quick to learn. But because it's a new unknown language, the TRACE_EVENT
>> will become less readable, less reachable for newcomers in TRACE_EVENT.
>
> I tried to avoid this too, but when I started writing a tool in C that
> would parse the format file, I found that the printf was horrible.
>
> Note, I will still keep the TP_printk() macro, that will not change. The
> new macro is TP_FORMAT() that preforms the tags. Thus, if you really want
> it to print out, you can use TP_printk, but the user space tools that read
> the binary will not know how to read it unless the printk is simple.
>
> I really want to keep this language simple. If anyone has any better
> ideas, I'm all for it.
>
> I barfed when I saw this in irq_handler_entry:
>
> print fmt: "irq=%d handler=%s", REC->irq, (char *)((void *)REC + REC->__data_loc_name)
>

I barfed too when I saw this. Introducing a new format is
very meaningful. And this print format looks well.
Good Work!

I'm trying to write user-space tools. Could you tell me your tools'
developing status? And the aim of these tools? Will it be public?

I'm wandering whether I should stop this trying.

Lai.



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