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s390/spinlock: disabled compare-and-delay by default 

Until we have hard performance data about the effects of CAD in the
spinlock loop disable the instruction by default.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2015-02-19 17:53:16 +01:00
parent 4ba2815d3b
commit 61b0b01686
1 changed files with 7 additions and 5 deletions
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12
arch/s390/kernel/early.c
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@ -393,17 +393,19 @@ static __init void detect_machine_facilities(void)
S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC;
if (test_facility(129))
S390_lowcore.machine_flags |= MACHINE_FLAG_VX;
if (test_facility(128))
S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
#endif
}
static int __init nocad_setup(char *str)
static int __init cad_setup(char *str)
{
S390_lowcore.machine_flags &= ~MACHINE_FLAG_CAD;
int val;
get_option(&str, &val);
if (val && test_facility(128))
S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
return 0;
}
early_param("nocad", nocad_setup);
early_param("cad", cad_setup);
static int __init cad_init(void)
{