Re: [RFC] gcc feature request: Moving blocks into sections

Linus Torvalds
2013-08-05T18:20:31Z

On Mon, Aug 5, 2013 at 10:55 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> My main concern is with tracepoints. Which on 90% (or more) of systems
> running Linux, is completely off, and basically just dead code, until
> someone wants to see what's happening and enables them.

The static_key_false() approach with minimal inlining sounds like a
much better approach overall. Sure, it might add a call/ret, but it
adds it to just the unlikely tracepoint taken path.

Of course, it would be good to optimize static_key_false() itself -
right now those static key jumps are always five bytes, and while they
get nopped out, it would still be nice if there was some way to have
just a two-byte nop (turning into a short branch) *if* we can reach
another jump that way..For small functions that would be lovely. Oh
well.

Linus