On Mon, 2017-03-20 at 14:14 -0700, Matthew Wilcox wrote: > I recently introduced memset32() / memset64(). I've done implementations > for x86 & ARM; akpm has agreed to take the patchset through his tree. > Do you fancy doing a powerpc version? Minchan Kim got a 7% performance > increase with zram from switching to the optimised version on x86.
+Anton Thanks Matthew ! > Here's the development git tree: > http://git.infradead.org/users/willy/linux-dax.git/shortlog/refs/heads/memfill > (most recent 7 commits) > > ARM probably offers the best model for you to work from; it's basically > just a case of jumping into the middle of your existing memset loop. > It was only three instructions to add support to ARM, but I don't know > PowerPC well enough to understand how your existing memset works. > I'd start with something like this ... note that you don't have to > implement memset64 on 32-bit; I only did it on ARM because it was free. > It doesn't look free for you as you only store one register each time > around the loop in the 32-bit memset implementation: > > 1: stwu r4,4(r6) > bdnz 1b > > (wouldn't you get better performance on 32-bit powerpc by unrolling that > loop like you do on 64-bit?) > > diff --git a/arch/powerpc/include/asm/string.h > b/arch/powerpc/include/asm/string.h > index da3cdffca440..c02392fced98 100644 > --- a/arch/powerpc/include/asm/string.h > +++ b/arch/powerpc/include/asm/string.h > @@ -6,6 +6,7 @@ > #define __HAVE_ARCH_STRNCPY > #define __HAVE_ARCH_STRNCMP > #define __HAVE_ARCH_MEMSET > +#define __HAVE_ARCH_MEMSET_PLUS > #define __HAVE_ARCH_MEMCPY > #define __HAVE_ARCH_MEMMOVE > #define __HAVE_ARCH_MEMCMP > @@ -23,6 +24,18 @@ extern void * memmove(void *,const void *,__kernel_size_t); > extern int memcmp(const void *,const void *,__kernel_size_t); > extern void * memchr(const void *,int,__kernel_size_t); > > +extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t); > +static inline void *memset32(uint32_t *p, uint32_t v, __kernel_size_t n) > +{ > > + return __memset32(p, v, n * 4); > +} > + > +extern void *__memset64(uint64_t *, uint64_t v, __kernel_size_t); > +static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n) > +{ > > + return __memset64(p, v, n * 8); > +} > + > #endif /* __KERNEL__ */ > > > #endif /* _ASM_POWERPC_STRING_H */
