Messages in this thread | | | Date | Thu, 30 Oct 2008 20:26:21 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC][PATCH] Make ftrace able to trace function return |
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* Steven Rostedt <rostedt@goodmis.org> wrote:
> gcc -c -finstrument-functions traceme.c
> This is not 5 extra bytes but 27 extra bytes for a total of 32 bytes > at every function. Also note that this also adds these calls to > inline functions as well. We could easly stop that by adding > "notrace" to the inline define (which I've done). > > But this would make the patching a bit more difficult (not > impossible). But it will bloat the image quite a bit.
yeah, i too knew it was expensive, but didnt realize it's this bloaty. It's a non-starter really.
How reliable can we make Frederic's trampoline approach? Especially with the opt-in function filters of dyn-ftrace, there's real value in the trampoline approach IMO (we could display real function cost, etc.), and the runtime cost should be OK as long we dont probe a ton of functions all the time. (and it's optional anyway)
Ingo
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