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Commit 61e98ebf authored by Anton Blanchard's avatar Anton Blanchard Committed by Michael Ellerman
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powerpc: Remove static branch prediction in atomic{, 64}_add_unless 



I see quite a lot of static branch mispredictions on a simple
web serving workload. The issue is in __atomic_add_unless(), called
from _atomic_dec_and_lock(). There is no obvious common case, so it
is better to let the hardware predict the branch.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent bb85fb58

arch/powerpc/include/asm/atomic.h

+2 −2
Original line number Diff line number Diff line
@@ -233,7 +233,7 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u) 
	PPC_ATOMIC_ENTRY_BARRIER

"1:	lwarx	%0,0,%1		# __atomic_add_unless\n\

	cmpw	0,%0,%3 \n\

	beq-	2f \n\

	beq	2f \n\

	add	%0,%2,%0 \n"

	PPC405_ERR77(0,%2)

"	stwcx.	%0,0,%1 \n\
@@ -539,7 +539,7 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u) 
	PPC_ATOMIC_ENTRY_BARRIER

"1:	ldarx	%0,0,%1		# __atomic_add_unless\n\

	cmpd	0,%0,%3 \n\

	beq-	2f \n\

	beq	2f \n\

	add	%0,%2,%0 \n"

"	stdcx.	%0,0,%1 \n\

	bne-	1b \n"