Re: [PATCHv8 02/34] lib/vdso: make do_hres and do_coarse as __always_inline

Vincenzo Frascino
2020-01-10T12:18:15Z

On 1/10/20 12:02 PM, Thomas Gleixner wrote:
> Vincenzo Frascino <vincenzo.frascino-5wv7dgnIgG8@public.gmane.org> writes:
>> On 1/10/20 11:42 AM, Thomas Gleixner wrote:
>>>>> +» » /*·goto·allows·to·avoid·extra·inlining·of·do_hres.·*/
>>>>> +» » goto·out_hres;
>>>>
>>>> What is the performance impact of "goto out_hres"?
>>>
>>> On x86 it's invisible at least in my limited testing.
>>
>> On arm64 as well based on mine as well. Shall we keep the code more readable
>> here (without goto)?
>
> The delta patch below makes it readable again and also avoids the double
> inlining. Quick testing shows no difference.
>

I tested it on arm64 and it does not show any difference as well.
I vote for it :)

> Thanks,
>
> tglx
>
> 8<---------------
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -98,17 +98,15 @@ static __maybe_unused int
> msk = 1U << clock;
> if (likely(msk & VDSO_HRES)) {
> vd = &vd[CS_HRES_COARSE];
> -out_hres:
> - return do_hres(vd, clock, ts);
> } else if (msk & VDSO_COARSE) {
> do_coarse(&vd[CS_HRES_COARSE], clock, ts);
> return 0;
> } else if (msk & VDSO_RAW) {
> vd = &vd[CS_RAW];
> - /* This goto avoids extra inlining of do_hres. */
> - goto out_hres;
> + } else {
> + return -1;
> }
> - return -1;
> + return do_hres(vd, clock, ts);
> }
>
> static __maybe_unused int
>

--
Regards,
Vincenzo