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| author |   Brian Gerst <brgerst@gmail.com> | 2010-09-09 18:17:26 +0200 |
|---|---|---|
| committer |   Tejun Heo <tj@kernel.org> | 2010-09-10 10:56:47 +0200 |
| commit | db7829c6cc32f3c0c9a324118d743acb1abff081 (patch) | |
| tree | dd40c271aeda63843819072c753af74fefc1413c /arch/x86/include/asm/percpu.h | |
| parent | percpu: clear memory allocated with the km allocator (diff) | |
| download | linux-dev-db7829c6cc32f3c0c9a324118d743acb1abff081.tar.xz linux-dev-db7829c6cc32f3c0c9a324118d743acb1abff081.zip | |
x86, percpu: Optimize this_cpu_ptr
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.
tj: * Beefed up the comment a bit and renamed in-macro temp variable
to match neighboring macros.
* Folded fix for const pointer case found in linux-next.
* Fixed sparse notation.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/percpu.h')
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index cd28f9ad910d..f899e01a8ac9 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -47,6 +47,20 @@ #ifdef CONFIG_SMP #define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x #define __my_cpu_offset percpu_read(this_cpu_off) + +/* + * Compared to the generic __my_cpu_offset version, the following + * saves one instruction and avoids clobbering a temp register. + */ +#define __this_cpu_ptr(ptr) \ +({ \ + unsigned long tcp_ptr__; \ + __verify_pcpu_ptr(ptr); \ + asm volatile("add " __percpu_arg(1) ", %0" \ + : "=r" (tcp_ptr__) \ + : "m" (this_cpu_off), "0" (ptr)); \ + (typeof(*(ptr)) __kernel __force *)tcp_ptr__; \ +}) #else #define __percpu_arg(x) "%P" #x #endif |