From 61b0b01686d482205db14987826e1a11dd17d65c Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Thu, 19 Feb 2015 17:53:16 +0100
Subject: [PATCH] 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>
---
arch/s390/kernel/early.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 70a3294509018..4427ab7ac23af 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -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)
{
--
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