this_cpu_ptr 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.
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 Changelog V2: 1. Use this_cpu_read directly instead of ref to field of per-cpu variable. 2. Patch5 about ftrace is dropped from this series. 3. Add new patch9 to replace get_cpu;per_cpu_ptr;put_cpu with this_cpu_add opt. 4. For preemption disable case, use __this_cpu_read instead. $ git diff --stat b77bc2069d1e437d5a1a71bb5cfcf4556ee40015 drivers/clocksource/arm_generic.c | 2 +- kernel/padata.c | 5 ++--- kernel/rcutree.c | 2 +- kernel/trace/blktrace.c | 2 +- kernel/trace/trace.c | 4 +--- net/batman-adv/main.h | 4 +--- net/core/flow.c | 4 +--- net/openvswitch/datapath.c | 4 ++-- net/openvswitch/vport.c | 5 ++--- net/rds/ib_recv.c | 2 +- net/xfrm/xfrm_ipcomp.c | 7 +++---- 11 files changed, 16 insertions(+), 25 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
