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SubjectRe: [PATCH 3/4] powerpc32: memset(0): use cacheable_memzero
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On Tue, 2015-05-12 at 15:32 +0200, Christophe Leroy wrote:
> cacheable_memzero uses dcbz instruction and is more efficient than
> memset(0) when the destination is in RAM
>
> This patch renames memset as generic_memset, and defines memset
> as a prolog to cacheable_memzero. This prolog checks if the byte
> to set is 0 and if the buffer is in RAM. If not, it falls back to
> generic_memcpy()
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> arch/powerpc/lib/copy_32.S | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/lib/copy_32.S b/arch/powerpc/lib/copy_32.S
> index cbca76c..d8a9a86 100644
> --- a/arch/powerpc/lib/copy_32.S
> +++ b/arch/powerpc/lib/copy_32.S
> @@ -12,6 +12,7 @@
> #include <asm/cache.h>
> #include <asm/errno.h>
> #include <asm/ppc_asm.h>
> +#include <asm/page.h>
>
> #define COPY_16_BYTES \
> lwz r7,4(r4); \
> @@ -74,6 +75,18 @@ CACHELINE_MASK = (L1_CACHE_BYTES-1)
> * to set them to zero. This requires that the destination
> * area is cacheable. -- paulus
> */
> +_GLOBAL(memset)
> + cmplwi r4,0
> + bne- generic_memset
> + cmplwi r5,L1_CACHE_BYTES
> + blt- generic_memset
> + lis r8,max_pfn@ha
> + lwz r8,max_pfn@l(r8)
> + tophys (r9,r3)
> + srwi r9,r9,PAGE_SHIFT
> + cmplw r9,r8
> + bge- generic_memset
> + mr r4,r5

max_pfn includes highmem, and tophys only works on normal kernel
addresses.

If we were to point memset_io, memcpy_toio, etc. at noncacheable
versions, are there any other callers left that can reasonably point at
uncacheable memory?

-Scott




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