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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/oprofile/backtrace.c
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@@ -32,24 +32,6 @@ typedef struct
u64 *prev_pfs_loc; /* state for WAR for old spinlock ool code */
} ia64_backtrace_t;
#if (__GNUC__ == 3 && __GNUC_MINOR__ < 3)
/*
* Returns non-zero if the PC is in the spinlock contention out-of-line code
* with non-standard calling sequence (on older compilers).
*/
static __inline__ int in_old_ool_spinlock_code(unsigned long pc)
{
extern const char ia64_spinlock_contention_pre3_4[] __attribute__ ((weak));
extern const char ia64_spinlock_contention_pre3_4_end[] __attribute__ ((weak));
unsigned long sc_start = (unsigned long)ia64_spinlock_contention_pre3_4;
unsigned long sc_end = (unsigned long)ia64_spinlock_contention_pre3_4_end;
return (sc_start && sc_end && pc >= sc_start && pc < sc_end);
}
#else
/* Newer spinlock code does a proper br.call and works fine with the unwinder */
#define in_old_ool_spinlock_code(pc) 0
#endif
/* Returns non-zero if the PC is in the Interrupt Vector Table */
static __inline__ int in_ivt_code(unsigned long pc)
{
@@ -80,7 +62,7 @@ static __inline__ int next_frame(ia64_backtrace_t *bt)
*/
if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
bt->frame.pfs_loc = &bt->regs->ar_pfs;
bt->prev_pfs_loc = (in_old_ool_spinlock_code(bt->frame.ip) ? bt->frame.pfs_loc : NULL);
bt->prev_pfs_loc = NULL;
return unw_unwind(&bt->frame) == 0;
}