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authorMichael Ellerman <mpe@ellerman.id.au>2014-01-15 07:14:28 (GMT)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2014-01-28 03:45:43 (GMT)
commit3405d230b374b6923878b21b8d708d7db1f734ef (patch)
tree789bd76b9c2b5a0f00bbe1f410927cf23debf96d /arch/powerpc
parentf7d98d18a01ece2863984d4fb5ae949b18b02715 (diff)
powerpc: Add support for the optimised lockref implementation
This commit adds the architecture support required to enable the optimised implementation of lockrefs. That's as simple as defining arch_spin_value_unlocked() and selecting the Kconfig option. We also define cmpxchg64_relaxed(), because the lockref code does not need the cmpxchg to have barrier semantics. Using Linus' test case[1] on one system I see a 4x improvement for the basic enablement, and a further 1.3x for cmpxchg64_relaxed(), for a total of 5.3x vs the baseline. On another system I see more like 2x improvement. [1]: http://marc.info/?l=linux-fsdevel&m=137782380714721&w=4 Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/Kconfig1
-rw-r--r--arch/powerpc/include/asm/cmpxchg.h1
-rw-r--r--arch/powerpc/include/asm/spinlock.h5
3 files changed, 7 insertions, 0 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index fa39517..6ca5d5c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -139,6 +139,7 @@ config PPC
select OLD_SIGACTION if PPC32
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_IRQ_EXIT_ON_IRQ_STACK
+ select ARCH_USE_CMPXCHG_LOCKREF if PPC64
config GENERIC_CSUM
def_bool CPU_LITTLE_ENDIAN
diff --git a/arch/powerpc/include/asm/cmpxchg.h b/arch/powerpc/include/asm/cmpxchg.h
index e245aab..d463c68 100644
--- a/arch/powerpc/include/asm/cmpxchg.h
+++ b/arch/powerpc/include/asm/cmpxchg.h
@@ -300,6 +300,7 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
cmpxchg_local((ptr), (o), (n)); \
})
+#define cmpxchg64_relaxed cmpxchg64_local
#else
#include <asm-generic/cmpxchg-local.h>
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 5f54a74..5162f8c 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -54,6 +54,11 @@
#define SYNC_IO
#endif
+static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+ return lock.slock == 0;
+}
+
/*
* This returns the old value in the lock, so we succeeded
* in getting the lock if the return value is 0.

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