[PATCH] use tsc on 1 cpu smp

[Pete Wyckoff]

Use num_online_cpus() instead of num_present_cpus() as the
parameter to check when deciding if TSC is good enough.  Thus
explicitly booting with maxcpus=1 will let us use the TSC even on
a dual-processor machine.  This helps reduce gettimeofday
overheads on our dual Opteron nodes immensely (30 us vs 0.5 us).

Signed-off-by: Pete Wyckoff <pw@xxxxxxx>
---
 arch/x86/kernel/tsc_64.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c
index 9c70af4..5f2e91f 100644
--- a/arch/x86/kernel/tsc_64.c
+++ b/arch/x86/kernel/tsc_64.c
@@ -235,7 +235,7 @@ __cpuinit int unsynchronized_tsc(void)
 	}
 
 	/* Assume multi socket systems are not synchronized */
-	return num_present_cpus() > 1;
+	return num_online_cpus() > 1;
 }
 
 int __init notsc_setup(char *s)
-- 
1.5.3.7

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