From: Shan Wei Date: Tue, 13 Nov 2012 12:36:00 +0000 (+0800) Subject: net: xfrm: use __this_cpu_read per-cpu helper X-Git-Tag: omap-for-v3.8/fixes-for-merge-window-v4-signed~45^2~244^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7c83bcbfaf5c848018680a499aa6b50b32f3085;p=pandora-kernel.git net: xfrm: use __this_cpu_read per-cpu helper this_cpu_ptr/this_cpu_read is faster than per_cpu_ptr(p, smp_processor_id()) and can reduce memory accesses. The latter helper needs to find the offset for current cpu, and needs more assembler instructions which objdump shows in following. this_cpu_ptr relocates and address. this_cpu_read() relocates the address and performs the fetch. this_cpu_read() saves you more instructions since it can do the relocation and the fetch in one instruction. per_cpu_ptr(p, smp_processor_id())： 1e: 65 8b 04 25 00 00 00 00 mov %gs:0x0,%eax 26: 48 98 cltq 28: 31 f6 xor %esi,%esi 2a: 48 c7 c7 00 00 00 00 mov $0x0,%rdi 31: 48 8b 04 c5 00 00 00 00 mov 0x0(,%rax,8),%rax 39: c7 44 10 04 14 00 00 00 movl $0x14,0x4(%rax,%rdx,1) this_cpu_ptr(p) 1e: 65 48 03 14 25 00 00 00 00 add %gs:0x0,%rdx 27: 31 f6 xor %esi,%esi 29: c7 42 04 14 00 00 00 movl $0x14,0x4(%rdx) 30: 48 c7 c7 00 00 00 00 mov $0x0,%rdi Signed-off-by: Shan Wei Signed-off-by: Steffen Klassert --- Reading git-diff-tree failed