Messages in this thread Patch in this message | | | Date | Fri, 29 Aug 2008 13:00:12 +0100 | From | "Jan Beulich" <> | Subject | [PATCH] x86: improve instruction selection/placement for ticket locks |
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Reduce the amount of partial register accesses in the NR_CPUS < 256 case, and slightly weaken resource dependencies in the other case.
Signed-off-by: Jan Beulich <jbeulich@novell.com> Cc: Nick Piggin <npiggin@suse.de>
--- include/asm-x86/spinlock.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
--- linux-2.6.27-rc5/include/asm-x86/spinlock.h 2008-08-21 14:37:34.000000000 +0200 +++ 2.6.27-rc5-x86-spinlock-insns/include/asm-x86/spinlock.h 2008-08-19 12:43:22.000000000 +0200 @@ -21,8 +21,10 @@ #ifdef CONFIG_X86_32 # define LOCK_PTR_REG "a" +# define REG_PTR_MODE "k" #else # define LOCK_PTR_REG "D" +# define REG_PTR_MODE "q" #endif #if defined(CONFIG_X86_32) && \ @@ -89,19 +91,17 @@ static __always_inline void __ticket_spi static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock) { - int tmp; - short new; + int tmp, new; - asm volatile("movw %2,%w0\n\t" + asm volatile("movzwl %2, %0\n\t" "cmpb %h0,%b0\n\t" + "leal 0x100(%" REG_PTR_MODE "0), %1\n\t" "jne 1f\n\t" - "movw %w0,%w1\n\t" - "incb %h1\n\t" "lock ; cmpxchgw %w1,%2\n\t" "1:" "sete %b1\n\t" "movzbl %b1,%0\n\t" - : "=&a" (tmp), "=Q" (new), "+m" (lock->slock) + : "=&a" (tmp), "=&q" (new), "+m" (lock->slock) : : "memory", "cc"); @@ -160,8 +160,8 @@ static __always_inline int __ticket_spin "movl %0,%1\n\t" "roll $16, %0\n\t" "cmpl %0,%1\n\t" + "leal 0x00010000(%" REG_PTR_MODE "0), %1\n\t" "jne 1f\n\t" - "addl $0x00010000, %1\n\t" "lock ; cmpxchgl %1,%2\n\t" "1:" "sete %b1\n\t"
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