On 10/07/2010 10:40 PM, tip-bot for Zhao Yakui wrote:
> Commit-ID: 68f4d5a00adaab33b136fce2c72d5c377b39b0b0
> Gitweb: http://git.kernel.org/tip/68f4d5a00adaab33b136fce2c72d5c377b39b0b0
> Author: Zhao Yakui <yakui.zhao@xxxxxxxxx>
> AuthorDate: Fri, 8 Oct 2010 09:47:33 +0800
> Committer: H. Peter Anvin <hpa@xxxxxxxxx>
> CommitDate: Thu, 7 Oct 2010 21:23:09 -0700
>
> x86, setup: Use string copy operation to optimze copy in kernel compression
>
> The kernel decompression code parses the ELF header and then copies
> the segment to the corresponding destination. Currently it uses slow
> byte-copy code. This patch makes it use the string copy operations
> instead.
>
> In the test the copy performance can be improved very significantly after using
> the string copy operation mechanism.
> 1. The copy time can be reduced from 150ms to 20ms on one Atom machine
> 2. The copy time can be reduced about 80% on another machine
> The time is reduced from 7ms to 1.5ms when using 32-bit kernel.
> The time is reduced from 10ms to 2ms when using 64-bit kernel.
>
> Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
> LKML-Reference: <1286502453-7043-1-git-send-email-yakui.zhao@xxxxxxxxx>
> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
> ---
> arch/x86/boot/compressed/misc.c | 29 +++++++++++++++++++++++------
> 1 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 8f7bef8..23f315c 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -229,18 +229,35 @@ void *memset(void *s, int c, size_t n)
> ss[i] = c;
> return s;
> }
> -
> +#ifdef CONFIG_X86_32
> void *memcpy(void *dest, const void *src, size_t n)
> {
> - int i;
> - const char *s = src;
> - char *d = dest;
> + int d0, d1, d2;
> + asm volatile(
> + "rep ; movsl\n\t"
> + "movl %4,%%ecx\n\t"
> + "rep ; movsb\n\t"
> + : "=&c" (d0), "=&D" (d1), "=&S" (d2)
> + : "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)
> + : "memory");
>
> - for (i = 0; i < n; i++)
> - d[i] = s[i];
> return dest;
> }
> +#else
> +void *memcpy(void *dest, const void *src, size_t n)
> +{
> + long d0, d1, d2;
> + asm volatile(
> + "rep ; movsq\n\t"
> + "movq %4,%%rcx\n\t"
> + "rep ; movsb\n\t"
> + : "=&c" (d0), "=&D" (d1), "=&S" (d2)
> + : "0" (n >> 3), "g" (n & 7), "1" (dest), "2" (src)
> + : "memory");
>
> + return dest;
> +}
> +#endif
>
> static void error(char *x)
> {
wonder if it would have problem with some old AMD K8 systems.
in amd.c
/* On C+ stepping K8 rep microcode works well for copy/memset */
if (c->x86 == 0xf) {
u32 level;
level = cpuid_eax(1);
if ((level >= 0x0f48 && level < 0x0f50) || level >= 0x0f58)
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
...
}
if (c->x86 >= 0x10)
set_cpu_cap(c, X86_FEATURE_REP_GOOD);
Yinghai
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