Messages in this thread | | | Date | Fri, 24 Jul 2020 13:48:11 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 2/2] kernel/trace: Remove function callback casts |
| |
On Fri, 24 Jul 2020 13:40:20 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Fri, 24 Jul 2020 13:36:56 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > Which BTW, is supported by the following architectures:
> > x86
Ah, you can lose support on x86 if you don't enable DYNAMIC_FTRACE, which is stupid to do. I only enabled disabling of DYNAMIC_FTRACE on x86 to test it, as not all architectures have it, and I currently only test on x86.
Without DYNAMIC_FTRACE enabled, you *always* call into the ftrace infrastructure for *every* function. This adds something like 15 to 20% overhead to the kernel. Did I say it was stupid to do so?
If you are going through all this work because some randconfig causes this warning because it enables CONFIG_FUNCTION_TRACER but without DYNAMIC_FTRACE enabled, then I strongly suggest you start spending your time elsewhere, because it will be a big NAK on my part to add all this intrusive code for a config used only for debugging the non DYNAMIC_FTRACE case.
-- Steve
| |