Re: [PATCH v2 22/25] powerpc32: move xxxxx_dcache_range() functions inline

[Joakim Tjernlund <joakim.tjernlund@transmode.se>]

On Tue, 2015-09-22 at 18:51 +0200, Christophe Leroy wrote:
> flush/clean/invalidate _dcache_range() functions are all very
> similar and are quite short. They are mainly used in __dma_sync()
> perf_event locate them in the top 3 consumming functions during
> heavy ethernet activity
>=20
> They are good candidate for inlining, as __dma_sync() does
> almost nothing but calling them
>=20
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> New in v2
>=20
>  arch/powerpc/include/asm/cacheflush.h | 55 +++++++++++++++++++++++++++--
>  arch/powerpc/kernel/misc_32.S         | 65 -----------------------------=
------
>  arch/powerpc/kernel/ppc_ksyms.c       |  2 ++
>  3 files changed, 54 insertions(+), 68 deletions(-)
>=20
> diff --git a/arch/powerpc/include/asm/cacheflush.h b/arch/powerpc/include=
/asm/cacheflush.h
> index 6229e6b..6169604 100644
> --- a/arch/powerpc/include/asm/cacheflush.h
> +++ b/arch/powerpc/include/asm/cacheflush.h
> @@ -47,12 +47,61 @@ static inline void __flush_dcache_icache_phys(unsigne=
d long physaddr)
>  }
>  #endif
> =20
> -extern void flush_dcache_range(unsigned long start, unsigned long stop);
>  #ifdef CONFIG_PPC32
> -extern void clean_dcache_range(unsigned long start, unsigned long stop);
> -extern void invalidate_dcache_range(unsigned long start, unsigned long s=
top);
> +/*
> + * Write any modified data cache blocks out to memory and invalidate the=
m.
> + * Does not invalidate the corresponding instruction cache blocks.
> + */
> +static inline void flush_dcache_range(unsigned long start, unsigned long=
 stop)
> +{
> +	void *addr =3D (void *)(start & ~(L1_CACHE_BYTES - 1));
> +	unsigned int size =3D stop - (unsigned long)addr + (L1_CACHE_BYTES - 1)=
;
> +	unsigned int i;
> +
> +	for (i =3D 0; i < size >> L1_CACHE_SHIFT; i++, addr +=3D L1_CACHE_BYTES=
)
> +		dcbf(addr);
> +	if (i)
> +		mb();	/* sync */
> +}

This feels optimized for the uncommon case when there is no invalidation.
I THINK it would be better to bail early and use do { .. } while(--i); inst=
ead.

 Jocke=