Tejon: Could you pick up this patchset? On Tue, 13 Nov 2012, Shan Wei wrote:
> 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. If you want to operate on rda(defined as per_cpu) > then you can only use this_cpu_ptr. 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 > > > > Changelog V4: > 1. [read|write]ing fields of struct rds_ib_cache_head using __this_cpu_* > operation for rds subsystem. > see patch2 > 2. fix bug in xfrm to read pointer. see patch3. > 3. avoid type cast in patch7. > > Changelog V3: > 1. use this_cpu_read directly read member of per-cpu variable, > so that droping the this_cpu_ptr operation. > 2. for preemption off and bottom halves off case, > use __this_cpu_read instead of this_cpu_read. > > 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 d4185bbf62a5d8d777ee445db1581beb17882a07 > drivers/clocksource/arm_generic.c | 2 +- > kernel/padata.c | 5 ++--- > kernel/rcutree.c | 2 +- > kernel/trace/blktrace.c | 2 +- > kernel/trace/trace.c | 5 +---- > net/batman-adv/main.h | 4 +--- > net/core/flow.c | 4 +--- > net/openvswitch/datapath.c | 4 ++-- > net/openvswitch/vport.c | 5 ++--- > net/rds/ib.h | 2 +- > net/rds/ib_recv.c | 24 +++++++++++++----------- > net/xfrm/xfrm_ipcomp.c | 8 +++----- > 12 files changed, 29 insertions(+), 38 deletions(-) >
