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authorChristoph Lameter <cl@linux.com>2010-12-08 18:22:55 +0300
committerTejun Heo <tj@kernel.org>2010-12-17 17:07:19 +0300
commit909ea96468096b07fbb41aaf69be060d92bd9271 (patch)
treea7e015edd96b5f674874fe78cdd889769e130a2a /include/linux/elevator.h
parent780f36d8b3fa9572f731d4fb85067b2e45e6f993 (diff)
downloadlinux-909ea96468096b07fbb41aaf69be060d92bd9271.tar.xz
core: Replace __get_cpu_var with __this_cpu_read if not used for an address.
__get_cpu_var() can be replaced with this_cpu_read and will then use a single read instruction with implied address calculation to access the correct per cpu instance. However, the address of a per cpu variable passed to __this_cpu_read() cannot be determined (since it's an implied address conversion through segment prefixes). Therefore apply this only to uses of __get_cpu_var where the address of the variable is not used. Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Hugh Dickins <hughd@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include/linux/elevator.h')
-rw-r--r--include/linux/elevator.h12
1 files changed, 3 insertions, 9 deletions
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 4fd978e7eb83..4d857973d2c9 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -195,15 +195,9 @@ enum {
/*
* io context count accounting
*/
-#define elv_ioc_count_mod(name, __val) \
- do { \
- preempt_disable(); \
- __get_cpu_var(name) += (__val); \
- preempt_enable(); \
- } while (0)
-
-#define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
-#define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
+#define elv_ioc_count_mod(name, __val) this_cpu_add(name, __val)
+#define elv_ioc_count_inc(name) this_cpu_inc(name)
+#define elv_ioc_count_dec(name) this_cpu_dec(name)
#define elv_ioc_count_read(name) \
({ \