Arnd Bergmann [off-list ref] writes:

On Mon, Dec 23, 2019 at 3:31 PM Christophe Leroy
[off-list ref] wrote:

quoted

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 <redacted>

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

Acked-by: Arnd Bergmann <arnd@arndb.de>

  https://lore.kernel.org/r/20191112012724.250792-3-dima@arista.com (local)

On the way to be applied.

Thanks,

        tglx

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