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

Richard Guenther
2009-01-09T18:59:22Z

On Fri, Jan 9, 2009 at 7:19 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> So we do have special issues. And exactly _because_ we have special issues
>> we should also expect that some compiler defaults simply won't ever really
>> be appropriate for us.
>
> I agree that the kernel needs quite different inlining heuristics
> than let's say a template heavy C++ program. I guess that is
> also where our trouble comes from -- gcc is more tuned for the
> later. Perhaps because the C++ programmers are better at working
> with the gcc developers?
>
> But it's also not inconceivable that gcc adds a -fkernel-inlining or
> similar that changes the parameters if we ask nicely. I suppose
> actually such a parameter would be useful for far more programs
> than the kernel.

I think that the kernel is a perfect target to optimize default -Os behavior for
(whereas template heavy C++ programs are a target to optimize -O2 for).
And I think we did a good job in listening to kernel developers if once in
time they tried to talk to us - GCC 4.3 should be good in compiling the
kernel with default -Os settings. We, unfortunately, cannot retroactively
fix old versions that kernel developers happen to like and still use.

Richard.