From: Christoph Hellwig <hch@infradead.org> To: Matteo Croce <mcroce@linux.microsoft.com> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Atish Patra <atish.patra@wdc.com>, Emil Renner Berthing <kernel@esmil.dk>, Akira Tsukamoto <akira.tsukamoto@gmail.com>, Drew Fustini <drew@beagleboard.org>, Bin Meng <bmeng.cn@gmail.com>, David Laight <David.Laight@aculab.com>, Guo Ren <guoren@kernel.org> Subject: Re: [PATCH v3 1/3] riscv: optimized memcpy Date: Mon, 21 Jun 2021 15:26:31 +0100 [thread overview] Message-ID: <YNChl0tkofSGzvIX@infradead.org> (raw) In-Reply-To: <20210617152754.17960-2-mcroce@linux.microsoft.com> On Thu, Jun 17, 2021 at 05:27:52PM +0200, Matteo Croce wrote: > +extern void *memcpy(void *dest, const void *src, size_t count); > +extern void *__memcpy(void *dest, const void *src, size_t count); No need for externs. > +++ b/arch/riscv/lib/string.c Nothing in her looks RISC-V specific. Why doesn't this go into lib/ so that other architectures can use it as well. > +#include <linux/module.h> I think you only need export.h. > +void *__memcpy(void *dest, const void *src, size_t count) > +{ > + const int bytes_long = BITS_PER_LONG / 8; > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > + const int mask = bytes_long - 1; > + const int distance = (src - dest) & mask; > +#endif > + union const_types s = { .u8 = src }; > + union types d = { .u8 = dest }; > + > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > + if (count < MIN_THRESHOLD) Using IS_ENABLED we can avoid a lot of the mess in this function. int distance = 0; if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { if (count < MIN_THRESHOLD) goto copy_remainder; /* copy a byte at time until destination is aligned */ for (; count && d.uptr & mask; count--) *d.u8++ = *s.u8++; distance = (src - dest) & mask; } if (distance) { ... > + /* 32/64 bit wide copy from s to d. > + * d is aligned now but s is not, so read s alignment wise, > + * and do proper shift to get the right value. > + * Works only on Little Endian machines. > + */ Normal kernel comment style always start with a: /* > + for (next = s.ulong[0]; count >= bytes_long + mask; count -= bytes_long) { Please avoid the pointlessly overlong line. And (just as a matter of personal preference) I find for loop that don't actually use a single iterator rather confusing. Wjy not simply: next = s.ulong[0]; while (count >= bytes_long + mask) { ... count -= bytes_long; }
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org> To: Matteo Croce <mcroce@linux.microsoft.com> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Atish Patra <atish.patra@wdc.com>, Emil Renner Berthing <kernel@esmil.dk>, Akira Tsukamoto <akira.tsukamoto@gmail.com>, Drew Fustini <drew@beagleboard.org>, Bin Meng <bmeng.cn@gmail.com>, David Laight <David.Laight@aculab.com>, Guo Ren <guoren@kernel.org> Subject: Re: [PATCH v3 1/3] riscv: optimized memcpy Date: Mon, 21 Jun 2021 15:26:31 +0100 [thread overview] Message-ID: <YNChl0tkofSGzvIX@infradead.org> (raw) In-Reply-To: <20210617152754.17960-2-mcroce@linux.microsoft.com> On Thu, Jun 17, 2021 at 05:27:52PM +0200, Matteo Croce wrote: > +extern void *memcpy(void *dest, const void *src, size_t count); > +extern void *__memcpy(void *dest, const void *src, size_t count); No need for externs. > +++ b/arch/riscv/lib/string.c Nothing in her looks RISC-V specific. Why doesn't this go into lib/ so that other architectures can use it as well. > +#include <linux/module.h> I think you only need export.h. > +void *__memcpy(void *dest, const void *src, size_t count) > +{ > + const int bytes_long = BITS_PER_LONG / 8; > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > + const int mask = bytes_long - 1; > + const int distance = (src - dest) & mask; > +#endif > + union const_types s = { .u8 = src }; > + union types d = { .u8 = dest }; > + > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > + if (count < MIN_THRESHOLD) Using IS_ENABLED we can avoid a lot of the mess in this function. int distance = 0; if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { if (count < MIN_THRESHOLD) goto copy_remainder; /* copy a byte at time until destination is aligned */ for (; count && d.uptr & mask; count--) *d.u8++ = *s.u8++; distance = (src - dest) & mask; } if (distance) { ... > + /* 32/64 bit wide copy from s to d. > + * d is aligned now but s is not, so read s alignment wise, > + * and do proper shift to get the right value. > + * Works only on Little Endian machines. > + */ Normal kernel comment style always start with a: /* > + for (next = s.ulong[0]; count >= bytes_long + mask; count -= bytes_long) { Please avoid the pointlessly overlong line. And (just as a matter of personal preference) I find for loop that don't actually use a single iterator rather confusing. Wjy not simply: next = s.ulong[0]; while (count >= bytes_long + mask) { ... count -= bytes_long; } _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2021-06-21 14:27 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-17 15:27 [PATCH v3 0/3] riscv: optimized mem* functions Matteo Croce 2021-06-17 15:27 ` Matteo Croce 2021-06-17 15:27 ` [PATCH v3 1/3] riscv: optimized memcpy Matteo Croce 2021-06-17 15:27 ` Matteo Croce 2021-06-18 14:06 ` kernel test robot 2021-06-18 14:06 ` kernel test robot 2021-06-18 14:06 ` kernel test robot 2021-06-21 14:26 ` Christoph Hellwig [this message] 2021-06-21 14:26 ` Christoph Hellwig 2021-06-22 8:19 ` David Laight 2021-06-22 8:19 ` David Laight 2021-06-22 22:53 ` Matteo Croce 2021-06-22 22:53 ` Matteo Croce 2021-06-22 22:00 ` Matteo Croce 2021-06-22 22:00 ` Matteo Croce 2021-06-22 0:14 ` Nick Kossifidis 2021-06-22 0:14 ` Nick Kossifidis 2021-06-22 23:35 ` Matteo Croce 2021-06-22 23:35 ` Matteo Croce 2021-06-23 9:48 ` Nick Kossifidis 2021-06-23 9:48 ` Nick Kossifidis 2021-06-17 15:27 ` [PATCH v3 2/3] riscv: optimized memmove Matteo Croce 2021-06-17 15:27 ` Matteo Croce 2021-06-21 14:28 ` Christoph Hellwig 2021-06-21 14:28 ` Christoph Hellwig 2021-06-22 0:46 ` Nick Kossifidis 2021-06-22 0:46 ` Nick Kossifidis 2021-06-30 4:40 ` kernel test robot 2021-06-30 4:40 ` kernel test robot 2021-06-30 4:40 ` kernel test robot 2021-06-17 15:27 ` [PATCH v3 3/3] riscv: optimized memset Matteo Croce 2021-06-17 15:27 ` Matteo Croce 2021-06-21 14:32 ` Christoph Hellwig 2021-06-21 14:32 ` Christoph Hellwig 2021-06-22 1:07 ` Nick Kossifidis 2021-06-22 1:07 ` Nick Kossifidis 2021-06-22 8:38 ` David Laight 2021-06-22 8:38 ` David Laight 2021-06-23 1:14 ` Matteo Croce 2021-06-23 1:14 ` Matteo Croce 2021-06-23 9:05 ` David Laight 2021-06-23 9:05 ` David Laight 2021-06-23 0:08 ` Matteo Croce 2021-06-23 0:08 ` Matteo Croce 2021-06-22 1:09 ` [PATCH v3 0/3] riscv: optimized mem* functions Nick Kossifidis 2021-06-22 1:09 ` Nick Kossifidis 2021-06-22 2:39 ` Guo Ren 2021-06-22 2:39 ` Guo Ren
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