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[IA64] implement ticket locks for Itanium

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Back in January 2008 Nick Piggin implemented "ticket" spinlocks
for X86 (See commit 314cdbefd1).

IA64 implementation has a couple of differences because of the
available atomic operations ... e.g. we have no fetchadd2 instruction
that operates on a 16-bit quantity so we make ticket locks use
a 32-bit word for each of the current ticket and now-serving values.

Performance on uncontended locks is about 8% worse than the previous
implementation, but this seems a good trade for determinism in the
contended case. Performance impact on macro-level benchmarks is in
the noise.

Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Tony Luck
2009-09-25 08:42:16 -07:00
parent 53cddfcc0e
commit 2c86963b09
6 changed files with 91 additions and 217 deletions
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20
arch/ia64/kernel/ia64_ksyms.c
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@ -84,26 +84,6 @@ EXPORT_SYMBOL(ia64_save_scratch_fpregs);
#include <asm/unwind.h>
EXPORT_SYMBOL(unw_init_running);
#ifdef ASM_SUPPORTED
# ifdef CONFIG_SMP
# if (__GNUC__ == 3 && __GNUC_MINOR__ < 3)
/*
* This is not a normal routine and we don't want a function descriptor for it, so we use
* a fake declaration here.
*/
extern char ia64_spinlock_contention_pre3_4;
EXPORT_SYMBOL(ia64_spinlock_contention_pre3_4);
# else
/*
* This is not a normal routine and we don't want a function descriptor for it, so we use
* a fake declaration here.
*/
extern char ia64_spinlock_contention;
EXPORT_SYMBOL(ia64_spinlock_contention);
# endif
# endif
#endif
#if defined(CONFIG_IA64_ESI) || defined(CONFIG_IA64_ESI_MODULE)
extern void esi_call_phys (void);
EXPORT_SYMBOL_GPL(esi_call_phys);