Commit | Line | Data |
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45efc5a3 PP |
1 | The +{macro-name}()+ and +v{macro-name}()+ utility macros were |
2 | developed to make user space tracing super simple, albeit with notable | |
3 | disadvantages compared to custom, full-fledged tracepoint providers: | |
4ddbd0b7 PP |
4 | |
5 | * All generated events have the same provider/event names. | |
6 | * There's no static type checking. | |
7 | * The only event field with user data you actually get, named `msg`, | |
8 | is a string potentially containing the values you passed to the | |
9 | macro using your own format. This also means that you cannot use | |
10 | filtering using a custom expression at run time because there are no | |
11 | isolated fields. | |
45efc5a3 PP |
12 | * Since +{macro-name}()+ and +v{macro-name}()+ use C standard |
13 | library's man:vasprintf(3) function in the background to format the | |
14 | strings at run time, their expected performance is lower than using | |
15 | custom tracepoint providers with typed fields, which do not require | |
16 | a conversion to a string. | |
4ddbd0b7 | 17 | * Generally, a string containing the textual representation of the |
45efc5a3 PP |
18 | user data fields is not as compact as binary fields in the resulting |
19 | trace. | |
4ddbd0b7 | 20 | |
45efc5a3 PP |
21 | Thus, +{macro-name}()+/+v{macro-name}()+ are useful for quick |
22 | prototyping and debugging, but should not be considered for any | |
23 | permanent/serious application instrumentation. | |
4ddbd0b7 | 24 | |
45efc5a3 PP |
25 | +v{macro-name}()+ does not have a `STAP_PROBEV()` call, because |
26 | `STAP_PROBEV()` does not support `va_list`. If you need it, you should | |
27 | emit this call yourself. | |
cfd56ee1 | 28 | |
4ddbd0b7 | 29 | See man:lttng-ust(3) to learn more about custom tracepoint providers. |