Re: [PATCH v2 4/8] powerpc/vdso32: inline __get_datapage()

[Christophe Leroy]

Hi Santosh,

Le 26/08/2019 Ã 07:44, Santosh Sivaraj a ÃcritÂ:
> Hi Christophe,
>
> Christophe Leroy <christophe.leroy@xxxxxx> 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@xxxxxx>
> > ---
> >   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