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

Thomas Gleixner
2020-01-10T12:02:25Z

Vincenzo Frascino <vincenzo.frascino@arm.com> 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.

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