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core: Replace __get_cpu_var with __this_cpu_read if not used for an address.

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__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>
This commit is contained in:
Christoph Lameter 2010-12-08 16:22:55 +01:00 • committed by Tejun Heo
parent 780f36d8b3
commit 909ea96468
13 changed files with 60 additions and 66 deletions
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12
include/linux/elevator.h
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@ -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) \
({ \