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[NET]: Disable NET_SCH_CLK_CPU for SMP x86 hosts

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Opterons with frequency scaling have fully unsynchronized TSCs
running at different frequencies, so using TSCs there is not a good idea. 
Also some other x86 boxes have this problem. gettimeofday should be good 
enough, so just disable it.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Andi Kleen 2005-10-13 14:41:44 -07:00 committed by David S. Miller
parent c8923c6b85
commit 34cb711ba9
1 changed files with 3 additions and 1 deletions
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net/sched/Kconfig
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@ -72,9 +72,11 @@ config NET_SCH_CLK_GETTIMEOFDAY
Choose this if you need a high resolution clock source but can't use
the CPU's cycle counter.
# don't allow on SMP x86 because they can have unsynchronized TSCs.
# gettimeofday is a good alternative
config NET_SCH_CLK_CPU
bool "CPU cycle counter"
depends on X86_TSC || X86_64 || ALPHA || SPARC64 || PPC64 || IA64
depends on ((X86_TSC || X86_64) && !SMP) || ALPHA || SPARC64 || PPC64 || IA64
help
Say Y here if you want to use the CPU's cycle counter as clock source.
This is a cheap and high resolution clock source, but on some