Messages in this thread | | | Date | Thu, 14 May 2015 10:50:07 +0200 | From | christophe leroy <> | Subject | Re: [PATCH 3/4] powerpc32: memset(0): use cacheable_memzero |
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Le 14/05/2015 02:55, Scott Wood a écrit : > 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. Is there any other simple way to determine whether an address is in RAM or not ?
I did that because of the below function from mm/mem.c
|int page_is_ram(unsigned long pfn) { #ifndef CONFIG_PPC64 /* XXX for now */ return pfn< max_pfn; #else unsigned long paddr= (pfn<< PAGE_SHIFT); struct memblock_region*reg;
for_each_memblock(memory, reg) if (paddr>= reg->base&& paddr< (reg->base+ reg->size)) return 1; return 0; #endif } |
> > 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? Do you mean we could just consider that memcpy() and memset() are called only with destination on RAM and thus we could avoid the check ? copy_tofrom_user() already does this assumption (allthought a user app could possibly provide a buffer located in an ALSA mapped IO area)
Christophe
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