lkml.org 
[lkml]   [2012]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subject[PATCH 0/9 v2] use efficient this_cpu_* helper
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 majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-11-02 17:21    [W:0.034 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site