Messages in this thread Patch in this message | | | From | Brian Gerst <> | Subject | [PATCH 1/2] x86, percpu: Optimize this_cpu_ptr | Date | Tue, 7 Sep 2010 07:41:09 -0400 |
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Allow arches to implement __this_cpu_ptr, and provide an x86 version.
Before: movq $foo, %rax movq %gs:this_cpu_off, %rdx addq %rdx, %rax
After: movq $foo, %rax addq %gs:this_cpu_off, %rax
The benefit is doing it in one less instruction and not clobbering a temporary register.
Signed-off-by: Brian Gerst <brgerst@gmail.com> --- arch/x86/include/asm/percpu.h | 11 +++++++++++ include/asm-generic/percpu.h | 9 +++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index cd28f9a..845343e 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -47,6 +47,17 @@ #ifdef CONFIG_SMP #define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x #define __my_cpu_offset percpu_read(this_cpu_off) + +/* shift a per-cpu pointer to the current cpu's version */ +#define __this_cpu_ptr(ptr) \ +({ \ + typeof(ptr) __ptr = (ptr); \ + __verify_pcpu_ptr(ptr); \ + asm volatile("add " __percpu_arg(1) ", %0" \ + : "+r" (__ptr) \ + : "m" (this_cpu_off)); \ + __ptr; \ +}) #else #define __percpu_arg(x) "%P" #x #endif diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h index b5043a9..5820fcb 100644 --- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -60,9 +60,14 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; #define __raw_get_cpu_var(var) \ (*SHIFT_PERCPU_PTR(&(var), __my_cpu_offset)) -#define this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, my_cpu_offset) +#ifndef __this_cpu_ptr #define __this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset) - +#endif +#ifdef CONFIG_DEBUG_PREEMPT +#define this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, my_cpu_offset) +#else +#define this_cpu_ptr(ptr) __this_cpu_ptr(ptr) +#endif #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA extern void setup_per_cpu_areas(void); -- 1.7.2.2
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