Re: [patch] measurements, numbers about CONFIG_OPTIMIZE_INLINING=y impact

Steven Rostedt
2009-01-09T21:33:04Z

On Fri, 9 Jan 2009, Theodore Tso wrote:

> I'm beginning to think that for the kernel, we should just simply
> remove CONFIG_OPTIMIZE_INLINING (so that inline means
> "always_inline"), and -fno-inline-functions
> -fno-inline-functions-called-one (so that gcc never inlines functions
> behind our back) --- and then we create tools that count how many times functions get used, and how big functions are, so that we can flag if some
> function really should be marked inline when it isn't or vice versa.
>
> But given that this is a very hard thing for an automated program
> todo, let's write some tools so we can easily put a human in the loop,
> who can add or remove inline keywords where it makes sense, and let's
> give up on gcc being able to "guess" correctly.
>
> For some things, like register allocation, I can accept that the
> compiler will usually get these things right. But whether or not to
> inline a function seems to be one of those things that humans (perhaps
> with some tools assist) can still do a better job than compilers.

Adding a function histogram in ftrace should be trivial. I can write one
up if you want. It will only count the functions not inlined.

-- Steve