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SubjectRe: [PATCH v3 4/8] powerpc/vdso32: inline __get_datapage()
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Hi Michael,

Le 22/11/2019 à 07:38, Michael Ellerman a écrit :
> Michael Ellerman <mpe@ellerman.id.au> writes:
>> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>>> __get_datapage() is only a few instructions to retrieve the
>>> address of the page where the kernel stores data to the VDSO.
>>>
>>> By inlining this function into its users, a bl/blr pair and
>>> a mflr/mtlr pair is avoided, plus a few reg moves.
>>>
>>> The improvement is noticeable (about 55 nsec/call on an 8xx)
>>>
>>> vdsotest before the patch:
>>> gettimeofday: vdso: 731 nsec/call
>>> clock-gettime-realtime-coarse: vdso: 668 nsec/call
>>> clock-gettime-monotonic-coarse: vdso: 745 nsec/call
>>>
>>> vdsotest after the patch:
>>> gettimeofday: vdso: 677 nsec/call
>>> clock-gettime-realtime-coarse: vdso: 613 nsec/call
>>> clock-gettime-monotonic-coarse: vdso: 690 nsec/call
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>
>> This doesn't build with gcc 4.6.3:
>>
>> /linux/arch/powerpc/kernel/vdso32/gettimeofday.S: Assembler messages:
>> /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:41: Error: unsupported relocation against __kernel_datapage_offset
>> /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:86: Error: unsupported relocation against __kernel_datapage_offset
>> /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:213: Error: unsupported relocation against __kernel_datapage_offset
>> /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:247: Error: unsupported relocation against __kernel_datapage_offset
>> make[4]: *** [arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
>
> Actually I guess it's binutils, which is v2.22 in this case.
>
> Needed this:
>
> diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
> index 12785f72f17d..0048db347ddf 100644
> --- a/arch/powerpc/include/asm/vdso_datapage.h
> +++ b/arch/powerpc/include/asm/vdso_datapage.h
> @@ -117,7 +117,7 @@ extern struct vdso_data *vdso_data;
> .macro get_datapage ptr, tmp
> bcl 20, 31, .+4
> mflr \ptr
> - addi \ptr, \ptr, __kernel_datapage_offset - (.-4)
> + addi \ptr, \ptr, (__kernel_datapage_offset - (.-4))@l
> lwz \tmp, 0(\ptr)
> add \ptr, \tmp, \ptr
> .endm
>

Are you still planning to getting this series merged ? Do you need any
help / rebase / re-spin ?

Christophe

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