[PATCH v2] eal: add build-time option to omit trace

[Morten Brørup]

> Could you share data with a real-world application of the elf size?
> 1)Without any change

Size of the statically linked executable on the target file system:
3,800,528 byte

> 2)Only disabling via __rte_trace_point_emit_header_generic() .. aka below
> patch.

3,572,032 byte

> 3)Full disable.

3,572,032 byte

> 
> I think, size command will spit out with different section's size.
> This data can be used to take decision and to know how much % it
> adding up?

I.e. trace adds 228,496 byte = 6.4 % to the size of this specific executable.

~200 KB might not seem as much, but this is just omitting one module.
If other unused modules also add ~200 KB, it adds up.

And I haven't done any significant additional memory footprint tuning.


> > > #define __rte_trace_point_emit_header_generic(t) \
> > > void *mem; \
> > > do { \
> > >   +      if (RTE_TRACE == 0) \
> > >   +             return \

Tested without the RTE_TRACE==0 check, simply:
  void *mem; \
  do { \
+         return; \
          const uint64_t val = rte_atomic_load_explicit(t, rte_memory_order_acquire); \

> > >         const uint64_t val = rte_atomic_load_explicit(t,
> > > rte_memory_order_acquire); \
> > >         if (likely(!(val & __RTE_TRACE_FIELD_ENABLE_MASK))) \
> > >                 return; \
> > >         mem = __rte_trace_mem_get(val); \
> > >         if (unlikely(mem == NULL)) \
> > >                 return; \
> > >         mem = __rte_trace_point_emit_ev_header(mem, val); \
> > > } while (0)

I don't understand why your method uses as little memory as mine...
My method should also omit the trace points themselves, with their names and numbers, and their initialization.

I haven't looked deeper into it.

If your method of omitting trace is as efficient as all my ifdefs, I also prefer your method.
Simpler is better.