On Mon, 9 Oct 2023 18:58:27 +0800 Yajun Deng <yajun.deng@xxxxxxxxx> wrote: > > C compiler decides to inline or not, depending on various factors. > > > > The most efficient (and small) code is generated by this_cpu_inc() > > version, allowing the compiler to inline it. > > > > If you copy/paste this_cpu_inc() twenty times, then the compiler > > would not inline the function anymore. Yes, if you want something to be visible by ftrace, it must not be inlined (as inlined functions are not function calls by definition). And as Eric stated, the compiler is perfectly allowed to inline something if it believes it will be more efficient. i.e. There may be code around the function call that could be more efficient if it wasn't change to parameters. If you want to make sure a function stays out of line, you must explicitly tell the compiler you want the function not to ever be inlined (hence the "noinline" attribute). > > > Got it. Thank you. Great. -- Steve
