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SubjectRe: [PATCH v2 4/8] powerpc/vdso32: inline __get_datapage()
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Hi Santosh,

Le 26/08/2019 à 07:44, Santosh Sivaraj a écrit :
> Hi Christophe,
>
> 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>
>> ---
>> arch/powerpc/kernel/vdso32/cacheflush.S | 10 +++++-----
>> arch/powerpc/kernel/vdso32/datapage.S | 29 ++++-------------------------
>> arch/powerpc/kernel/vdso32/datapage.h | 11 +++++++++++
>> arch/powerpc/kernel/vdso32/gettimeofday.S | 13 ++++++-------
>> 4 files changed, 26 insertions(+), 37 deletions(-)
>> create mode 100644 arch/powerpc/kernel/vdso32/datapage.h
>
> The datapage.h file should ideally be moved under include/asm, then we can use
> the same for powerpc64 too.

I have a more ambitious project indeed.

Most of the VDSO code is duplicated between vdso32 and vdso64. I'm
aiming at merging everything into a single source code.

This means we would have to generate vdso32.so and vdso64.so out of the
same source files. Any idea on how to do that ? I'm not too good at
creating Makefiles. I guess we would have everything in
arch/powerpc/kernel/vdso/ and would have to build the objects twice,
once in arch/powerpc/kernel/vdso32/ and once in arch/powerpc/kernel/vdso64/

Christophe

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