From: Andi Kleen Date: Thu, 13 Oct 2005 21:41:44 +0000 (-0700) Subject: [NET]: Disable NET_SCH_CLK_CPU for SMP x86 hosts X-Git-Tag: v2.6.14-rc5~64 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=34cb711ba922f53cca45443b8c3c1078873cf599;p=linux-2.6 [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 Signed-off-by: David S. Miller --- diff --git a/net/sched/Kconfig b/net/sched/Kconfig index 45d3bc0812..81510da317 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