Re: [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time

Steven Rostedt
2018-03-28T19:38:19Z

On Wed, 28 Mar 2018 15:32:20 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> -#define __DO_TRACE(tp, proto, args, cond, rcucheck) \
> +#define __DO_TRACE(name, proto, args, cond, rcucheck) \
> do { \
> struct tracepoint_func *it_func_ptr; \
> void *it_func; \
> @@ -140,7 +140,7 @@ extern void syscall_unregfunc(void);
> if (rcucheck) \
> rcu_irq_enter_irqson(); \
> rcu_read_lock_sched_notrace(); \
> - it_func_ptr = rcu_dereference_sched((tp)->funcs); \
> + it_func_ptr = rcu_dereference_sched(__trace_##name##_funcs); \

What we lose in data size, we may make up for in text (which is even
more important). This will remove a dereference in the hot path.

I'll make a few builds and run size on the vmlinux images to see how
this pans out.

-- Steve

> if (it_func_ptr) { \
> do { \