doc/man/tracef-tracelog-limitations.txt

   1 The +{macro-name}()+ utility macro was developed to make user space
   2 tracing super simple, albeit with notable disadvantages compared to
   3 custom, full-fledged tracepoint providers:
   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.
  12   * Since +{macro-name}()+ uses C standard library's man:vasprintf(3)
  13     function in the background to format the strings at run time, its
  14     expected performance is lower than using custom tracepoint providers
  15     with typed fields, which do not require a conversion to a string.
  16   * Generally, a string containing the textual representation of the
  17     user data fields is not as compact as binary fields in the
  18     resulting trace.
  19
  20 Thus, +{macro-name}()+ is useful for quick prototyping and debugging, but
  21 should not be considered for any permanent/serious application
  22 instrumentation.
  23
  24 +v{macro-name}()+ does not have a `STAP_PROBEV()` call, because `STAP_PROBEV()`
  25 does not support `va_list`. If you need it, you should emit this call yourself.
  26
  27 See man:lttng-ust(3) to learn more about custom tracepoint providers.