+choice
+ prompt "Packet scheduler clock source"
+ depends on NET_SCHED
+ default NET_SCH_CLK_JIFFIES
+ help
+ Packet schedulers need a monotonic clock that increments at a static
+ rate. The kernel provides several suitable interfaces, each with
+ different properties:
+
+ - high resolution (us or better)
+ - fast to read (minimal locking, no i/o access)
+ - synchronized on all processors
+ - handles cpu clock frequency changes
+
+ but nothing provides all of the above.
+
+config NET_SCH_CLK_JIFFIES
+ bool "Timer interrupt"
+ help
+ Say Y here if you want to use the timer interrupt (jiffies) as clock
+ source. This clock source is fast, synchronized on all processors and
+ handles cpu clock frequency changes, but its resolution is too low
+ for accurate shaping except at very low speed.
+
+config NET_SCH_CLK_GETTIMEOFDAY
+ bool "gettimeofday"
+ help
+ Say Y here if you want to use gettimeofday as clock source. This clock
+ source has high resolution, is synchronized on all processors and
+ handles cpu clock frequency changes, but it is slow.
+
+ Choose this if you need a high resolution clock source but can't use
+ the CPU's cycle counter.
+
+config NET_SCH_CLK_CPU
+ bool "CPU cycle counter"
+ depends on X86_TSC || X86_64 || 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
+ architectures it is not synchronized on all processors and doesn't
+ handle cpu clock frequency changes.
+
+ The useable cycle counters are:
+
+ x86/x86_64 - Timestamp Counter
+ alpha - Cycle Counter
+ sparc64 - %ticks register
+ ppc64 - Time base
+ ia64 - Interval Time Counter
+
+ Choose this if your CPU's cycle counter is working properly.
+
+endchoice
+