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authorAndi Kleen <ak@suse.de>2005-10-13 14:41:44 -0700
committerDavid S. Miller <davem@davemloft.net>2005-10-13 14:41:44 -0700
commit34cb711ba922f53cca45443b8c3c1078873cf599 (patch)
tree2b120d59460047caff9546d68f445626947d47fc
parentc8923c6b852d3a97c1faad0566e38fca330375a7 (diff)
[NET]: Disable NET_SCH_CLK_CPU for SMP x86 hosts
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>
-rw-r--r--net/sched/Kconfig4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 45d3bc0812c..81510da3179 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -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