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

From: Thomas Gleixner <[email-masked]>
Date: Fri, 10 Jan 2020 22:07:48 +0100

Arnd Bergmann <[email-masked]> writes:
> On Mon, Dec 23, 2019 at 3:31 PM Christophe Leroy
> <[email-masked]> 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 <[email-masked]>
>
> Good idea, I can see how this ends up being an improvement
> for most of the callers.
>
> Acked-by: Arnd Bergmann <[email-masked]>

  https://lore.kernel.org/r/[email-masked]

On the way to be applied.

Thanks,

        tglx

_______________________________________________
linux-arm-kernel mailing list
[email-masked]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel