From 6cb9a8350aee789100a365794272ed20cc8f2401 Mon Sep 17 00:00:00 2001 From: Zachary Amsden Date: Mon, 5 Mar 2007 00:30:35 -0800 Subject: [PATCH] vmi: sched clock paravirt op fix The custom_sched_clock hook is broken. The result from sched_clock needs to be in nanoseconds, not in CPU cycles. The TSC is insufficient for this purpose, because TSC is poorly defined in a virtual environment, and mostly represents real world time instead of scheduled process time (which can be interrupted without notice when a virtual machine is descheduled). To make the scheduler consistent, we must expose a different nature of time, that is scheduled time. So deprecate this custom_sched_clock hack and turn it into a paravirt-op, as it should have been all along. This allows the tsc.c code which converts cycles to nanoseconds to be shared by all paravirt-ops backends. It is unfortunate to add a new paravirt-op, but this is a very distinct abstraction which is clearly different for all virtual machine implementations, and it gets rid of an ugly indirect function which I ashamedly admit I hacked in to try to get this to work earlier, and then even got in the wrong units. Signed-off-by: Zachary Amsden Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/tsc.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'arch/i386/kernel/tsc.c') diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index 3082a418635..c9c9d54c91f 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -14,6 +14,7 @@ #include #include #include +#include #include "mach_timer.h" @@ -102,9 +103,6 @@ unsigned long long sched_clock(void) { unsigned long long this_offset; - if (unlikely(custom_sched_clock)) - return (*custom_sched_clock)(); - /* * Fall back to jiffies if there's no TSC available: */ @@ -113,7 +111,7 @@ unsigned long long sched_clock(void) return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); /* read the Time Stamp Counter: */ - rdtscll(this_offset); + get_scheduled_cycles(this_offset); /* return the value in ns */ return cycles_2_ns(this_offset); -- cgit v1.2.3-70-g09d2