Re: [PATCH 4/9] powerpc: inline ip_fast_csum()

[Denis Kirjanov]

On 9/22/15, Christophe Leroy <christophe.leroy@xxxxxx> wrote:
> In several architectures, ip_fast_csum() is inlined
> There are functions like ip_send_check() which do nothing
> much more than calling ip_fast_csum().
> Inlining ip_fast_csum() allows the compiler to optimise better

Hi Christophe,
I did try it and see no difference on ppc64. Did you test with socklib
with modified loopback and if so do you have any numbers?
>
> Suggested-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
>  arch/powerpc/include/asm/checksum.h | 46
> +++++++++++++++++++++++++++++++------
>  arch/powerpc/lib/checksum_32.S      | 21 -----------------
>  arch/powerpc/lib/checksum_64.S      | 27 ----------------------
>  arch/powerpc/lib/ppc_ksyms.c        |  1 -
>  4 files changed, 39 insertions(+), 56 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/checksum.h
> b/arch/powerpc/include/asm/checksum.h
> index afa6722..56deea8 100644
> --- a/arch/powerpc/include/asm/checksum.h
> +++ b/arch/powerpc/include/asm/checksum.h
> @@ -9,16 +9,9 @@
>   * 2 of the License, or (at your option) any later version.
>   */
>
> -/*
> - * This is a version of ip_compute_csum() optimized for IP headers,
> - * which always checksum on 4 octet boundaries.  ihl is the number
> - * of 32-bit words and is always >= 5.
> - */
>  #ifdef CONFIG_GENERIC_CSUM
>  #include <asm-generic/checksum.h>
>  #else
> -extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
> -
>  /*
>   * computes the checksum of a memory block at buff, length len,
>   * and adds in "sum" (32-bit)
> @@ -137,6 +130,45 @@ static inline __wsum csum_add(__wsum csum, __wsum
> addend)
>  #endif
>  }
>
> +/*
> + * This is a version of ip_compute_csum() optimized for IP headers,
> + * which always checksum on 4 octet boundaries.  ihl is the number
> + * of 32-bit words and is always >= 5.
> + */
> +static inline __wsum ip_fast_csum_nofold(const void *iph, unsigned int
> ihl)
> +{
> +	u32 *ptr = (u32 *)iph + 1;
> +#ifdef __powerpc64__
> +	unsigned int i;
> +	u64 s = *(__force u32 *)iph;
> +
> +	for (i = 0; i < ihl - 1; i++, ptr++)
> +		s += *ptr;
> +	s += (s >> 32);
> +	return (__force __wsum)s;
> +
> +#else
> +	__wsum sum, tmp;
> +
> +	asm("mtctr %3;"
> +	    "addc %0,%4,%5;"
> +	    "1:lwzu %1, 4(%2);"
> +	    "adde %0,%0,%1;"
> +	    "bdnz 1b;"
> +	    "addze %0,%0;"
> +	    : "=r"(sum), "=r"(tmp), "+b"(ptr)
> +	    : "r"(ihl - 2), "r"(*(u32 *)iph), "r"(*ptr)
> +	    : "ctr", "xer", "memory");
> +
> +	return sum;
> +#endif
> +}
> +
> +static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
> +{
> +	return csum_fold(ip_fast_csum_nofold(iph, ihl));
> +}
> +
>  #endif
>  #endif /* __KERNEL__ */
>  #endif
> diff --git a/arch/powerpc/lib/checksum_32.S
> b/arch/powerpc/lib/checksum_32.S
> index 6d67e05..0d7eba3 100644
> --- a/arch/powerpc/lib/checksum_32.S
> +++ b/arch/powerpc/lib/checksum_32.S
> @@ -20,27 +20,6 @@
>  	.text
>
>  /*
> - * ip_fast_csum(buf, len) -- Optimized for IP header
> - * len is in words and is always >= 5.
> - */
> -_GLOBAL(ip_fast_csum)
> -	lwz	r0,0(r3)
> -	lwzu	r5,4(r3)
> -	addic.	r4,r4,-2
> -	addc	r0,r0,r5
> -	mtctr	r4
> -	blelr-
> -1:	lwzu	r4,4(r3)
> -	adde	r0,r0,r4
> -	bdnz	1b
> -	addze	r0,r0		/* add in final carry */
> -	rlwinm	r3,r0,16,0,31	/* fold two halves together */
> -	add	r3,r0,r3
> -	not	r3,r3
> -	srwi	r3,r3,16
> -	blr
> -
> -/*
>   * computes the checksum of a memory block at buff, length len,
>   * and adds in "sum" (32-bit)
>   *
> diff --git a/arch/powerpc/lib/checksum_64.S
> b/arch/powerpc/lib/checksum_64.S
> index f3ef354..f53f4ab 100644
> --- a/arch/powerpc/lib/checksum_64.S
> +++ b/arch/powerpc/lib/checksum_64.S
> @@ -18,33 +18,6 @@
>  #include <asm/ppc_asm.h>
>
>  /*
> - * ip_fast_csum(r3=buf, r4=len) -- Optimized for IP header
> - * len is in words and is always >= 5.
> - *
> - * In practice len == 5, but this is not guaranteed.  So this code does
> not
> - * attempt to use doubleword instructions.
> - */
> -_GLOBAL(ip_fast_csum)
> -	lwz	r0,0(r3)
> -	lwzu	r5,4(r3)
> -	addic.	r4,r4,-2
> -	addc	r0,r0,r5
> -	mtctr	r4
> -	blelr-
> -1:	lwzu	r4,4(r3)
> -	adde	r0,r0,r4
> -	bdnz	1b
> -	addze	r0,r0		/* add in final carry */
> -        rldicl  r4,r0,32,0      /* fold two 32-bit halves together */
> -        add     r0,r0,r4
> -        srdi    r0,r0,32
> -	rlwinm	r3,r0,16,0,31	/* fold two halves together */
> -	add	r3,r0,r3
> -	not	r3,r3
> -	srwi	r3,r3,16
> -	blr
> -
> -/*
>   * Computes the checksum of a memory block at buff, length len,
>   * and adds in "sum" (32-bit).
>   *
> diff --git a/arch/powerpc/lib/ppc_ksyms.c b/arch/powerpc/lib/ppc_ksyms.c
> index f5e427e..8cd5c0b 100644
> --- a/arch/powerpc/lib/ppc_ksyms.c
> +++ b/arch/powerpc/lib/ppc_ksyms.c
> @@ -19,7 +19,6 @@ EXPORT_SYMBOL(strncmp);
>  #ifndef CONFIG_GENERIC_CSUM
>  EXPORT_SYMBOL(csum_partial);
>  EXPORT_SYMBOL(csum_partial_copy_generic);
> -EXPORT_SYMBOL(ip_fast_csum);
>  #endif
>
>  EXPORT_SYMBOL(__copy_tofrom_user);
> --
> 2.1.0
>
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