Re: [RFC PATCH v2 05/10] lib: vdso: inline do_hres()

[Arnd Bergmann]

On Mon, Dec 23, 2019 at 3:31 PM Christophe Leroy
<christophe.leroy@xxxxxx> wrote:
>
> do_hres() is called from several places, so GCC doesn't inline
> it at first.
>
> do_hres() takes a struct __kernel_timespec * parameter for
> passing the result. In the 32 bits case, this parameter corresponds
> to a local var in the caller. In order to provide a pointer
> to this structure, the caller has to put it in its stack and
> do_hres() has to write the result in the stack. This is suboptimal,
> especially on RISC processor like powerpc.
>
> By making GCC inline the function, the struct __kernel_timespec
> remains a local var using registers, avoiding the need to write and
> read stack.
>
> The improvement is significant on powerpc.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

Good idea, I can see how this ends up being an improvement
for most of the callers.

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>